I'd be tempted to go with Souray right now, just because he's a better player than Rivet. Seems like most of the time guys who get the C are one of the best player on the team, and usually leaders in the room too. The habs don't really have one guy who stands out like Koivu does at the moment, but I think Souray comes closest. Rivet is a close second.
Maybe it's better if I put it this way: I think Rivet deserves it, but I think Souray would be the guy who actually ends up getting it.
Future is confusing, with Chipchura, Higgins and Komisarek all looking like potential candidates. Personally I think Chipchura has the best shot, but it's really a crapshoot.