Guild Wars is still selling around 200 000 copies per quarter. That's pretty darn good sales considering they haven't released a game for some time and ArenaNet's only game is Guild Wars.
Yep, Guild Wars still gong strong.
Plus, ANet indicated some exciting plans this year - with several Live project teams on the go doing updates / improvements and several content releases planned during the course of the year, to keep people busy while they are busy developing GW2.