Eagle eyed OXM have spotted a job listing on the Obsidian website for a level designer to work on a "unique next generation game." Obsidian staff have mentioned how they would love to work on a Fallout: New Vegas 2 but "unique" would imply their new game isn't a sequel or established IP.
That rules out another single-player Knights of the Old Republic game too, but that seemed really unlikely anyway. Alpha Protocol 2? Probably not (hey, I liked Alpha Protocol!) A new IP would be under wraps for a while and let's be honest, no one's really going to confirm a bunch of next-gen titles until after E3.
There are also job listings for UI/user experience artist but neither job really gives us any clues as to what the game might be, compared to a role like multiplayer programmer or suchlike. Considering Obsidian are going to be making their Kickstarter game Project Eternity, I think it'll be a while before we hear confirmation about their new game actually is.