I think when Federer and Djokovic want a title more than anything, they lose. In sports, the more 'worked up' you are about a result, the harder it is to unleash your best level. Federer spoke so much about how badly he wanted Wimbledon last year, and he lost in the QF. And then earlier this year there was all the hype because he'd won 26 straight matches heading into the AO semi vs Nadal, so Federer's hopes were at an all-time high. Doesn't seem to help. And Djokovic last year was all about Roland Garros, and he lost in 4 sets in the semi. Now this year Federer is all about the Olympics, and its on grass, the surface Federer has lost at QF of the last 2 Wimbledons. And note that Federer has lost 3 times in the 1st Round of Wimbledon. So despite having a great prime on grass, it could be the surface he declines at first, because it was the surface he struggled on most early in his career. There may not be a connection, but the results certainly indicate that Federer is now a better hardcourt and clay player than grasscourt player.
I think whoever wins Roland Garros will likely win Wimbledon, as long as it is a convincing Roland Garros victory. Last year, Nadal did not win Roland Garros in a convincing manner. Was probably his worst Roland Garros ever apart from 2009. But this year, he looks like 2010 Nadal, actually even more aggressive than 2010. Maybe to do with the racquet change. Maybe he's just decided to go for broke in order to knock Djokovic off the court. Or maybe its a simple matter of his motivation being greater simply because of 2011. His motivation was great in 2010 after the disappointing 2009. That's the pattern. Maybe Nadal doesn't respond well to long periods of success. It may take his fighting spirit away. He is driven by new challenges.