The thing is, that's a bit like saying the next expansion of WoW is being "delayed" because Blizzard's production and resources are being spent on developing Diablo and Starcraft.

I just don't buy that argument. If a game is as popular as Guild Wars, then it should be worthwhile for a given developer to work on more than one product at a time.

GW2 is, in effect, a new game. But the old game, GW1, still has a lot of life left in it -- or would have, if ArenaNet invested in it. At the very least they should have subcontracted with another developer to work on expansion to GW1 while they focused on GW2. I think there was definitely more money to be made that way.