If you look at the actual number of copies sold to the number of players still playing guildwars today, I would assume that roughly half have left the game and will either buy the expansion or wont. According to my personal experience a big number in this, who are currently dormant have only 1 or 2 level 20 characters on their account and most of them were never serious about PvP, most of these I am sure wont return to GW. A good number of them did PvP a lot and just left due to boredom or moved to a different game with their friends, these players will most likely return when expansion comes out.
Now lets look at the other half thats still active. I'd say that almost 90% people have played PvE chars at one point or another for unlocking skills or for just enjoying the game and then got into PvP. Only a few people who were used to playing games in an organised fashion(TS/Vent etc) were maybe in the other 10%. So a lot of people both PvE and PvP and a small amount proly only PvP or PvE. But almost all people who PvE exclusively and a sizable option that do both, have more than 1 account. Exclusive PvPers will almost certainly never buy another account, because of all the unlock/rank headaches.
With the current trend in Guildwars more and more people are going for PvP due to lack of stuff to do in PvE, some of these people will really start enjoying PvP cause it is a lot of fun and join the exclusive PvP/No second account group. So more and more people will go for PvP and many claim this is what arena net wants, right? Because Guildwars is not a RPG with the grind of levels and other stupid RPG stuff. I totally agree with these facts, the way the game has evolved and the way things are going to work in the expansion, its quite obvious that ultimately GW is going to be a PvP based game.
So where is the problem? This is the part that Anet should be worried about, its a possiblity imo, and would affect GW in a big way.
Factions comes out. 300 new skills, 1 or 2 slots for old players.. 4 for new ones. Level cap remains, this is enuff to turn off a few folks who were in GW for the character building aspect of it (PvE type character progression, not PvP type), so some customers lost here, but thats ok I guess cause they shudnt be playing guildwars anyway, for they misunderstood it as a common rpg. So letem go you say, what about the new missions/items/armor/skills and the new areas which would be awesome to look at. Most of the PvE/PvPers would buy atleast one copy to check it out, almost all PvP only guys will buy one copy. Some of the PvP/PvE guys realize the reason for level cap and would enjoy the expansion to ultimately join the PvP only section. But a lot of em will be dissapointed with the 1 character slot that comes from buying the expansion and will not upgrade their other accounts. They will also realize the fact that level cap, same armor/weapon stats are there to keep PvP balanced and the entire expansion is only a practice to enrich the PvP experience, with more skills/elites and classes. The things that make PvE are just a sideshow to all of this. So this PvP/PvE group will keep splitting into the PvP only people and those who will hesitantly buy the next expansion and quit after that.
But this is good you will say as ANET is getting a big PvP only base that are faithful and would buy every expansion that comes out. WRONG, the amount of people who wont expand their multiple accounts will already put a big dent in Anets profit. Those who buy one hesitantly and then quit will add to further losses. The poor Noobs who misunderstood GW and were dissatisfied with the Level cap are inevitable losses. But wait it gets worse, with more and more expansions coming out and lots of new skills, the PvP side will become more complex, thus making it harder for a new player to enter PvP. Look at the scenario at present, just go to tombs, I ask you what chance does a new player has of finding a team and actually enjoying the game? Look at it 3 expansions down the road, its going to be impossible for noobs, with only rank 15+ groups forming. The number of skills availible will be mind boggling. With all the PvE only players leaving and the PvP base growing, guildwars will already have a PvP based game tag on it. Anet will never even know what amount of potential customers it lost just because of that tag. They can try fixing the ranks, that will make PvP elites furious, some will drop out, causing more loss. In the end Anet will be left with a group of faithful PvPers who have paid for all the expansions of a non-subscription based game and would now like to enjoy it for as long as they want. The larger this crowd is, larger is the amount of money Anet will be spending to maintain the servers. If they make it subscription based, lot of poeple will leave. Those who will remain will rant endlessly about how anet went bad on their pact, affecting PR further.
No amount of publicity will fix this , because GW is already a popular game and 3 expansions down the line, the image that poeple will have about guildwars, will be permanent. Some people might argue that the PvP base will generate enough profit for Anet to make guildwars a success. Maybe, maybe not, but if they dont fix something that they know WILL cut down their profit margin, its not a sound business strategy imo. I hope they take some action to prevent this from happening. I can be a PvP'er or a PvE'er, my money is still in my pocket. They have to keep me happy if they want it

PS : The figures I have used might be inaccurate, but the general player behaviour based on what they do in GW is quite accurate, as reflected by many posts on these forums.