Thief 4 has been announced (or rather the website went online)!
I'm looking forward to it, even though I never played any of the other Thief games. I know it's about being stealthy and since Deus Ex Human Revolution, that's something I really like. And it's even made by the same studio, Eidos Montreal. Right now there's only the teaser website, but I hope they'll release a trailer soon.