I wasn't that surprised. Once I heard Sauber were in the hunt, I thought he'd end up there - he's probably only got one or two seasons left, nice way to see his career out in a competitive little car that should get him points regularly with a chance of a podium.
From what I read Massa had been offered the test/reserve driver position (which would do him the world of good, assuming Sauber do a reasonable amount of testing next year), but there was nothing on whether he'd accepted the position as yet.