The Next Lux Tenebras, of course, and the "DarkMod" a special mod created from zero, based on the Doom3 Engine (that will be opensourced on the future), inspired by one of the best game of ever "Thief" (ex Looking Glass Masterpiece, of you like games for PC, you *must* know Looking Glass).
If you are curious:
www.thedarkmod.com
I hope also that the next Frictional Game will have a true Stealth component in the gaming like, and possibily more, in the great Penumbra series.
I'm waiting also the next "Portal" episode (the first Portal was very original, smart and cool game), pity it was only for Windows :-(
(i'm gaming on Linux... I played all the Penumbra series on my Ubuntu Box :-) )