I can't imagine (and most reports seem to agree) that this would be a one off thing. Surely Malkmus has seen the example of the Pixies and figures their fans have disposable income now.
So there's another in the list of shocking reunions happening. How long til Bob and Grant decide there's a ton of money to be made in doing a reunion tour playing "New Day Rising" or "Zen Arcade" in their entirety?
At one point they (Slash and co.) were thinking of getting Sebastian Bach to sing for them. I'm not sure how serious that was, however. One of my favorite lines about G n' R was from Conan O'Brian after they played the MTV movie (or was it music)