looks like i'm a little late to this party. Roger getting back number 1 this year is highly highly unrealistic. We need to remember that he had a flawless end to 2011 winning 3 or 4 tournaments (didn't lose indoors) and having something like only 2 losses since Wimbledon through the end of the year and that boosted him up. Combine that with a decent-solid start of the year 2012 (again, winning titles including Indian Wells) and winning Wimbledon (that he lost in Quarters in the year before, more of a points boost) along with a combination of Djokovic failing to defend some tournaments, it lined up and he took over number 1 by a very small margin. Very small margin.
Now consider this year, he lost a ton of points end of 2012 because he couldn't defend his 2011 points, so already coming into 2012 in a deficit. And he's had a not-so-hot 2013 so far. (Not so hot is relative since we are talking about capturing #1 here). He has nothing to gain and everything to lose at Wimbledon this year which is arguably his best chance for a great performance.
He'd really have to win everything he plays, mainly the Grand Slams, and even then it will be a close call if someone like Djokovic can keep making finals and winning the Masters that Fed's skipping. Throw in Nadal back into the mix and consider that Nadal-Murray-Djokovic are by far the more consistent players day in day out, have about 5 years up on Federer and are in their "peak" 23-28 age.. yeah, hanging on to the top 4 should satisfy Fed as far as rankings goes. Shooting for Slams and tournament wins is good and I hope he does that. Forget the rankings. And if he is shooting for slams and tournament wins, he won't be dropping out of the top 4 anytime soon.