I really don't see it going down any time soon.. I mean.. Apple is a machine now, they have their whole mindset in place. Jobs built it up to be what it is today, I'm sure they can survive without him, even if for the long term. If anything, everyone's hooked on the iOS/iTunes juice.. ain't no stopping that addiction.
Who knows, Tim Cook or another CEO could lead Apple into Enterprise territory where Jobs cannot compete.
Also, please don't take this the wrong way but some rumors going around that Cook prefers men. Now, I don't care one way or the other but he needs to keep it far back in the closet if he actually BECOMES CEO, as this may hurt Apple in the long run.
There's an air of success about Apple/Jobs and I think its mostly due to the fact that Jobs has really never been part of any negativity in the media, and I'm talking the usual scandals, etc. If you have a small foul up as CEO your company goes down.