I currenlty have only one quest left to complete, and I am quite surprised that no other quests have been appearing for a very (about 2 months) time, even when I got the new achievements.
Well, I think that many people do not have any quests left. I am negligent quests, haha. But someday, I will be done with all of my quests too. And let's hope, by then (because I think that it's going to be a long time :P), that there will be new ones.
The basics of the game are still being designed and tested. You're allowed to play while it's closed to the public because you are Beta testers. Until the basic mechanisms work correctly, the devs have to spend their time fixing the broken parts
We'll get quests when the game is running smoothly. But until there's a basic game engine that works well, quests aren't a high priority for developers time. It's perfectly normal for that to be put on a back burner.
WindBorn speaks truth. I didn't take their words as sour at all. It's been this way for a while. Many quests are associated with skills as we learn them; once skills are learned, most of the quests dry up and we make our own fun and our own goals. I'm sure we'll see more quests eventually, but given that they're working on some major changes, this could take time.