As I said earlier, it will look much more likely once (if) he [Federer] gets #2 from Nadal.
Here's how much they will have to defend for the next few tournaments in the year:
DOHA AO DUB IW MI MC MD RO
Nadal - 9,595 90 360 - 600 600 1000 600 600
Federer -8,170 250 720 300 360 360 180 360 90
Assuming that they defend their points at Doha and Federer wins the AO, he will be just a measly 145 points shy from Nadal.
If this scenario plays out Fed could see himself as #2 as early as before march if he improves his final appearance in Dubai (that's if he's playing there too).
But anyway, if he closes out this point advantage with a win at Melbourne he wouldn't need to rush things as Nadal would be defending a string of final appearances with 600 points or more that could drop at any bad showing from him in these tournaments from IW to Rome.
Fed on the other hand has much to gain and improve specially at Monte Carlo and Rome where he defends just a measly 180 and 90 points respectively. Any short lead Nadal would have at this point could easily have been overtaken by Fed by just improving these two results.
The #2 ranking as it stands is a very volatile one and could change in an instant. If Federer overtakes it, it will completely change the tennis landscape.
For instance Nadal's chances at RG, which already don't look as good as they were in the past, would look even more daunting when he finds himself in the #3 seed, having to play either Novak in the semis or to go over Federer and then Novak in the finals.
And if he drops most of his points from RG that could give Federer a firm grasp at the #2 ranking until at least the end of the year.
Novak will have a lot to defend himself, so we will see how well he will fare at such an herculean task of defending all these points and how much of a chance he will give to whoever is at the #2 position to overtake him.