Hanley still has the most upside, no question. The other three guys seem to belong at 2B, but could probably be future SS's if groomed to be. Theo loves Pedroia, as he does Shoppach, Alvarez and Murton. I think these guys are untouchable and should provide a core set of players for the Sox future as the C, 2B, LF and SP.
The thing about Hanley is that he hasn't hit for much power, nor has he shown as much plate discipline as Theo would like. He may be traded once he gets a little older. I think his max upside would be around Edgar Renteria.