I agree with Murray winning the French Open. I think he's favourite unless Djokovic shows some form before then. Then Wawrinka, then Nadal 4th. No one else has a chance.
As for Wimbledon I think Murray, Federer, Djokovic are clear favourites with someone like Cilic or Dimitrov as dark horses.
USO could be anyone from Djokovic, Murray, Wawrinka, Federer, Nadal with a big hitting outsider like Cilic or Del Potro having a slight chance.