What makes you "think" that Federer will retire at 35? What ridiculous speculation. I would not be surprised if he retired at the end of this year especially if GS results are not good. He has zero to prove anymore.
well Roger has said in interviews he 'hopes' to play until then, for that long..... maybe he wasn't being 100# seriously but he said it!
Nadal, who KNOWS. so many unknown variables with him, health, interest in the sport, other hobbies, fishing......