2 Roland-Garros, 2 Australian open (slow hardcourt, first match in 5 sets and Fed was the most dominant during first 4 sets, last one in the only cold day of the fortnight, slowest possible conditions), 1 Wimbledon (9-7 in final set).
Nadal is 8-4 against Fed since that FO 2008 final (included)
bigger chance yes, far bigger, absolutely no. He can lose to many other players and so can Nadal (notably to Djokovic, and Nadal was near to losing in Wimbledon early rounds several times before the Rosol-match, like Federer against Falla or Benneteau)
But lets look at the numbers - majors only - since Federer's last win against Nadal (ie. after Wimbledon 2007):
a) Played Nadal five times, number of major titles - 0.
b) Not played Nadal 16 times, number of major titles wins - 6.
Looking at those figures, Federer's chances of winning a major increase a lot
when he doesn't meet Nadal...