I think so. He was actually close in Australia - up a set - close second set - the match never seemed inevitable, and I say this as a Nadal fan. I think Federer has had better tactics recently against Nadal.
Best of 5 is always tougher for Federer as executing his game plan vs Nadal over that long can get tiring but I think it'll happen. Potentially US Open. Hope not but gut feeling...
In fact, he was up a set and a break which has NEVER happened to him in a match against Nadal EVER. So he was close. If they meet at the USO and Fed's not annihilated from a long semi, he has a chance.
The thing is though, much like Australia, when they meet RN is always playing really well and seeing as how he's such a bad matchup, even on less favourable for RN surfaces, it's always a tough proposition for the Old man to beat Nadal.