I have Djokovic and Murray as favourites. Their HC play deserves it, imo. Nadal and Federer should not be counted out, by any means, but I consider them less likely winners. Still more likely than anyone else, though. A healthy Del Potro, if we get to see that, would be my 5th pick for a title contender. Ferrer? No, I can't see him win, although I expect him to do well again. Tsonga? Berdych? Can't really see them win either.
Janowicz I think will falter badly. He has done very well in Wimby and history tells ut such slam breakthroughs are often followed by a letdown. But he will return stronger later.