Job pages. They can be gold mines of information, if you're willing to look for it. No need for picks and drills, just a web browser and a mouse cursor.
Local dev portal Sumea recently noticed that Pandemic has placed new positions up on its website. A few of the role descriptions include this tidbit: "That's right, new IP. Freshly baked creative freedom and the chance to make your mark on a new, huge success." If that wasn't enough, the job requirements for the "Designer - Team A" position give us an idea of what the studio might be working on:
Open world / sandbox experience a plus. As is experience with LUA. We are a SCRUM based team, but even if you have never done the agile development thing before, we are sure you will fit right in.
Open world eh? I can't wait to see what it is!
Update: It's been suggested the IP is the new Batman game, long-rumoured to be in development at Pandemic. If that's that case, I'd hardly call it "new".