They will continue to come out with new skills for all the exsisting classes, and wile the probably more pressing matter will be making new skills for classes that you can get out of the next chapter, I wanted to focus on making new kinds of skills, and original additions to all of the classes, old and new.
I realy like the idea of Dual Wielding, but I think this is a good part of a new class rather than an exsisting one, and I'm not talking about dual daggers, although if no addition for true dual wielding is added, I would like for them to make daggers with Full length sword skins, so you can at least masqurade as a dual sword wielder.
But using a 2 handed sword and Axe isn't realy original enough to make a new class with, maybe a samurai with a katana, but as for most juggernaut swords and Axes for 2 handed use, I think this would be a better addition to Warrior. Because the damage of current sword/axe skills and the type of skills corolate with the attack damage and speed of current swords/axes, I think you should only be able to use skills which are made for 2 handed swords and axes accordingly, but they can share the same attribute as normal sword and axe, saving the need for new attributes. Thus Sword Mastery would increase your attack damage with Swords and 2 handed swords (all swords), and increase the effectiveness of all sword skills, but you would only be able to use 2 handed sword skills with a 2 handed sword, and likewise for normal swords. This would allow for a new kind of weapon, or rather a variation, and new skills. Best part, they could make it so in a certain chapter, all the sword skills learned are for 2 handed swords, so Warriors made in that chapter are unique from other chapters, wile old warriors can join this chapter and learn to use 2 handed swords as well. This also promotes begining players who have bought one new chapter to get other chapters, to unlock the full diversity of skills that even the original classes have.
Anet could split this and put 2handed sword addition in one chapter, and 2 handed axe in another, =D developer trick to spread out their content so it lasts longer. And they could also add a simular aspect for Assassin, allowing them to use a new kind of weapon with their dual wielding, like a Swallow (doulbe ended spear, or staff weapon with blades on both ends).
Along the lines of new weapons for all the casters, some 2 handed weapons with higher damage and slower attack rate would be good, along with a new look, like an Orb, or better, spectral/elemental essence which glows in your hands, that would be awsome for elementist, carrying a 2 handed... spectral essence, so it simply looked like mini fire shots were shooting directly out of his hand when he attacks. But more importantly, melee caster weapons of many designs for caster classes, they would damage and and use/have mods the same as staffs or wands, but they would have slightly higher damage and work at melee range, allowing for more effective touch based spell use.
OK, my next original skill type would be Channeling, not channeling attribute, but channelling skill type. This is a primary addition for Elementist, but it could be use in skills for other classes, or maybe a primary feature in a new class. Channeling skills would be a skill that is continuous, like a maintained enchantment, but it would cause an effect like a ward or DoT damage. Wile channeling, you cannot move, or cast other spells, you are devoting all of your action to maintaining an effect, so the combination of all of your action, ability to move, and some energy cost/maintenance would cause stronger effects than a normal maintained enchantment or DoT. Also, Channelling would have a much wider area of effect, between a location effect and an area effect (same radius as a spirits effect).
These would actually be better as a skill type for a new class, which would be able to maintain a party support, or deal a weakenning effect or damage on enemies from a vast range, but either way elementist should have a hand in this. Channeling can cost large amounts of energy, and even 2 or 3 maintenance cost, or have some weaker effects, but overall, they should be rather expensive, since they effect a massive radius. Channelling skills can be interrupted wile casting, and have very long cast times, ranging from at least 3 seconds to even 10 seconds, but after it has begun, the only way to stop them is to knock the player down, or kill him, and there are ways to avoid knockdown

For Elementist, skills like Rain of Fire, dealing Firestorm damage in an medium area(about 50% wider than location). I would suggest a 20-25 energy cost, exhaustion, and 2 point mantenance. An Air skill that causes healing winds to blow in an area(same as spirit), giving all teammates in the area 1 health regeneration, and knocking down enemies in the area once every 10 seconds, simular costs. A necromancer skill which Automaticly raises any corpses into a standard minion after 4 seconds in an area, and granting no degen on all allied minions in your effected area, costing 25 energy, and 33% health, plus degen of 2 or 3 health and mantenance of 1. There can be monk and ritualist skills which grant continous regen, or repetative healing, or defensive boosts. A ritualist channeling skill, Summon an ancestoral spirit upon yourself, granting 25% chance to evade attacks to all teammates in a vast area of effect(50% wider than a spirit), but doubling the damage you take on yourself, only costing 10 energy and 1 maintenance.
They could also make strong location effects, like an elementist skill which turns the ground in to magma at his location, dealing firestorm level damage per second, and causing crippling and burning to anyone who is in the location around him, 20-25 energy, exhaustion, and 3 maintenance. That is enough examples, either you like it or you don't, but I think it would be a great tool to many caster classes, and it would make Elementist alot more fun. If they made a new class around these skills, I think some kind of Singing Priest would be cool, if anyone here has watched Record of Lodoss War, and knows what the Priests of Myree are, then you would get the picture, better name hopefully though.
The next skill type would be Sacrificing, a new kind of sacrificing for necromancer, sacrifice your life. I got this inspiration from the monument to the Ancestoral Necromancer in Factions, he found his family and village slain, so he raised them all into minions, and then sacrificed his own life to set them on a war path into the enemy line. They can make Death sacrifice skills which use all corpses in your area and turn them into minions, including your own, special minions which are 4 levels stronger than normal bone horrors, and dont degen. Or you could sacrifice your life to raise a level 24 bone dragon, but it wouldn't just be a minion, you would be in control of it, it would have 8 preset skills and you would control it until it dies, if you are raised it also dies. They can also have Ritualist skills that sacrifice his life to raise an ancestoral spirit to fight for him, controled by you. If they make a Summoner class, I think this would be a good cost for a true summoned beast, although it is a bit extreme for a primary function.
Oh wait, I just remembered the other skill type I came up with, Skill robbery, for Mesmer, it is a new kind of interrupt, which stops the enemy from casting a spell, and automaticly makes the mesmer use the skill against them. One spell which interrupts only offensive spells, and automaticly throws it back at the caster, one which robs support skills and automaticly cast it on himself, or perhaps it will steal the support skill and allow him to use it once for free on his allies. And one elite which robs any skill for up to 15 seconds, when the mesmer robs the skill the enemy can't use it until the mesmer uses the skill, so the mesmer can wait til the time is up to hold the spell for the longest period of time, and the enemies skill doesn't start recharging til he gives it up. Lets say the mesmer accidentally robs a sword skill, he can't use it, but he can sure hold on to it til the time is up

Added.
A good alternate weapon for Ranger would be a arm mounted bow/crossbow, I'm not interested in mechanical crossbows because they actually have longer firing rates, but rather, a mini bow that is mounted to one arm, which allows for faster, short ranged vollies. Anyone Seen vampire hunter D, the eldest Marcs brother had one, it was mini bow attached to the right for arm, it is basicly a non mechanical crossbow. This would be a weapon for Ranger to exploit damage per hit enchantments and preperations, since it is faster then the fastest current bows, at about 60% more attack speed than short bow, but half the range of most bows, it would provide a close range "Blast Em" effect, basicly trading the majority of rangers attack range for pure ApS (attacks per second).
Another good addition to ranger would be to change the mods on the bow so the shaft determines the bow type, wile the string determines special effects (armor, enchantment, energy). Then make Quivers of arrows, which will determine the damage type, longer bleeding or poison, elemental damage, life or energy stealing. This way players can find a great bow and make it the type of bow they want with mods, and allow for a visible quiver. If the player doesn't equipt a quiver, the arrows are simply normal.