Yes, Eidos are still releasing it but our old friend Looking Glass Studios has...well, broken
Ion Storm are the developers this time round. Theres alot of mixed opinions but it looks VERY promising. Rather than the Dark Engine they're using Geforce's Unreal Engine in Thief 3, go here to have a look at what graphics this engine can create :
http://gamespot.com/gamespot/stories...898008,00.html
It's just one snapshot but I think it looks very nice.
Also Thief 3 *should* (well im hoping to god it does) have multiplayer capability - that will be very cool.