So we know for a fact that obsidian is working on an unannounced title with a major publisher (pleas note that it's not said that it's a new IP, although it could be). So far so good, but recently Obsidian commented this on Twitter.. Obsidian's only work with SEGA has been Alpha Protocol. So all this two vague hints lead to Alpha Protocol 2!
Disclaimer: For all we know, it could be something with Paizo (although I don't know if that counts as a major publisher), or anything else. Don't get your hopes to high.