Nothing has been announced yet. When Bethesda unveils a game they like to have a lot to say about it, usually with a large magazine preview. For now all we can really do is wait, although there are a lot of rumors about this wait being over soon.
New Vegas has an http://www.gamesas.com/bgsforums/index.php?showtopic=1062902 and all discussion pertaining to the game should be kept there.
Bethesda tend to keep things close to the chest untill weeks before release.
There's a New Vegas Forum in Fallout:General Forums, I suggest you check there.
Weeks is a bit hyperbolous, but yes Bethesda doesn't like to release much information during pre-production or early developement. If they can get away with it they won't release
any information, including the fact that they're working on the game, until they unveil it - although that obviously isn't the case here.