it's hard to tell really. Fed is pretty much a lock for wimbledon and US open (Tsonga and Djoko won't replicate their once in a lifetime performances
At tha AO he's vulnerable to nadal and djoko, but if he carries his form from late 2011 to the AO, he should win it. I say it's 60% chances of winning it.
Same for RG, although I think djoko won't ever be a real threat to him there, he might tire him at best. So fed's hope is for djoko to take out nadal (since nadal might fall to number 3 before RG) and then he can slaughter the serb
Anyway I think he still has a chance to take out nadal this year. The more they get old the more fed will have chances to take him out actually, since nadal's movement is crumbling faster than fed's. I say he has a 50% chance to win it.
Therefore Fed has plenty of chances to win 3. Trolls will hunt me forever if I say he can win 4, but we all have that thought in one corner of our brain.