If push came to shove I woud much rather Andy drew Federer in the SF than Djokovic. Reasons being, Murray has played outstanding this year when up against Federer, not so much Djokovic.
You even had to think about it?
Of course Federer's the better opponent.
I think Andy is a decent price for the French right now considering the current state of Nadal, I'd rather flutter on that.
Considering last year he was behind Nadal, Djokovic, Federer, Ferrer and Berdych on that surface (and possibly Del Potro) I'd consider it a long shot, Nadal or no Nadal.
I wouldn't rule him out competing for it in the future though. As Andy himself pointed out last year, it tends to be the older players who fare well on the clay, with no-one really breaking through on that surface.
I think Wimbledon is easily his best chance of another Slam - mainly because it's Djokovic's least favourite surface.