I'm not convinced Djoker can stay № 1 till October - he's not that good of a number one.
He's more of a computer number one type: consistent, but not dominant front runner type who amasses far more point relative to the one ranked below him.
However I do believe some time in 2014 (or later) he will catch up with Nadal.
Maybe you don't know this: but it is mathematically impossible for Novak to lose his #1 before the 13th of May. This means that even if Novak doesn't play at all
and Roger wins every tournament he plays or Murray wins every tournament he plays, they still can't pass Novak. And that's because Novak has 25.86% more points than Roger and 52.35% more points than Andy.
Everything Novak earns from now until Madrid will be used to secure his #1 beyond May 13th... He'll catch up with Nadal in October. Wait and see.