Obsidian is teasing "Project X", with the main web page replaced with a snake insignia and the number "4", along with an uncredited quote.
Clicking through takes you to the Obsidian forums - specifically for "
Project X Speculation & Discussion" It goes on to say "This is a forum for Obsidian's next RPG endeavor. So secret not even its project codename is yet being revealed. Speculate here…".
So, speculate away!
More information.