After IW (provided Rainerer will win today), Nole will have 12.670 points, Nadal 10.175, and Federer 9.350.
So, just a little over 3.000 points between 1st and 3rd. Up until the end of Wimby, Nole defends 5.970, Nadal 5.345 and Fed 2.510, if my math is correct. So, I tell you, If Federer wins Wimbledon, I´m stating today, 18-03-2012, that he will be Nº1 imediately after that, even without the Olympics or the US Masters Series and US Open (and even if he decided not to play Monte Carlo, as he did).
Fed making the RG final and defending all those points is far from guaranteed. Novak and Nadal are still favourites to defend a lot of their points and Fed is still not favoured to win Wimbledon - he's lost in the quarters the last two years. One of Nadal or Novak may falter, but both? Unlikely.