Guildwars always was the equivilent of a singleplayer game anyway, it's a CO-RPG, not really an MMORPG. Don't let that stop you though. Go ahead and pick them up and enjoy them. Just don't go in anticipating it'll be a regular MMO like WoW.
I mean it's like a singleplayer game in the fact that you can complete it all on your own with NPC henchmen, which is what a lot of people tend to end up doing without the support of a guild or group of friends. There is still plenty of people around, not so much at the random towns/outposts, but at the large cities and trading centres it is packed.