It's hard to tell the full list, but GT5 is obviously the favourite to finish top. I reckon Uncharted 2 will pull ahead of MGS4 into second, but then it's going to have to compete with Final Fantasy Vs XIII for second imo. Those Japan sales should help FF pull ahead.
Agent is an interesting prospect too, current rumours suggest it's going to be Sony's big exclusive for Christmas 2010, and we've seen how Rockstar can sell games already. I see no reason that game can't be 5m+ if we assume 'the best' possible circumstances.
I think there is quite a while left in this gen though, so there will n odoubt be hits we dont know about yet.