It's coming to PC in 2014, it seems very likely it will be a title for next-gen consoles also.
The game is planned to be 20% bigger than Skyrim. It will be built on CD Projekt Red's new game engine and there's a tonne more info from GI's reveal in this Neogaf thread: http://www.neogaf.com/forum/showthread.php?t=511690
Here's GI magazine's cover:
and some video coverage: