Personally, I think he's staying. It's real easy to spend other teams money but the economics don't make a whole lot of sense. Assuming the Steelers tender Wallace, teams will value his worth and make an offer that they know the Steelers won't match. That's all fine and dandy but they're not going to break their own bank for a receiver who's sole attribute is speed. If the money isn't bad enough, teams will also have to give up their first round pick. That in itself is a high price to pay.
Maybe I'm underestimating Wallace's value but his production in the second half of the season should make teams pause before making an outrageous offer.
But then again, what do I know?