Better build a shrine to Tim Schafer. Notch just provides ze moniez (from what I gathered).
First off, I seriously doubt that Notch and Schafer would ever collaborate on a game. Notch has no experience in basically anything past Minecraft. A game that, no matter how you see it, is filled with incredibly deep flaws and a game he's since stopped working on. The game's design is now on one of his coworkers last time I checked. Then there's Scrolls which no one would ever care about if it wasn't for Minecraft.
Second off, I don't even see how a collaboration would be helpful. Notch isn't exactly a genius game designer. He hasn't made anything on the scale of a retail release. He's basically made a game, released it as imperfect, then continually finished development while it's already out. Something acceptable for digital distributed PC games but it would never fly with anything else. Psychonauts 2 would probably be an entire Schafer game and I doubt Mojang would ever be involved at all.
Plus I'm not exactly a fan of Notch. He's always come off to me as trying to be the Shingeru Miyamoto of indie gaming when there's so many other devs who I would say made a larger impact (Pixel of Cave Story fame, Garry Newman of Garry's Mod, and so on). But that's just me.