Higher number of party members?

I also heard the party size is now increased, will it be increased to 10?

I haven't heard that, but then again I just heard about this new Guild Wars game everyone is excited about!

Confirmation link? Support from the community? Is this speculation or fact?

I think a few missions have 10 maximum, yes. I'm not possitave though.

In the preview videos I have seen at least 10, it could be higher but I dont see it very probable.

Almost all of the longer preview videos show groups of ten going around doing stuff. There will be alliance battles which will be 12 against 12 but it will be divided up into 3 groups of 4. In these you'll probably be able to heal or cast allied spells on the people from the other 2 groups, that is if your groups spawn anywhere near eachother. But since they keep saying it's 3 groups of 4 you might not be able to see the other 2 group's health bars in your party window and probably not be able to use skills on them that target "all party members". Such as Heal Party or Order of the Vampire. This is speculation of course, we'll have to wait to be sure.

The 3 x 4 battle groups was mentioned by Gaille in another thread. I've heard nothing official on the other stuff, so ..... will wait and see.