Part of me wants to ask "Why are we all still discussing this?" but then I remember where I am and who you all are. I don't mean that in a bad nor condescending way, but nevertheless it goes to show how much the public is tying Apple -- for good or ill -- directly to Steve.
Apple's future success lies in the fact that technology and the state of the art has advanced as much as it has. The fact that Steve has particularly good taste (in general; there are certainly exceptions) and is a "vision" guy means the entire industry, and not just the community of employees at Apple, have a better sense of how to create products which please the general public. I also think Apple has shown up enough major companies that the industry kind of "gets" the fact that pleasing the customer is not just the right thing to do, but it can be the insanely profitable thing to do.
What I mean by all of this is that I think there are enough people who've come of age in the industry during Steve's second tenure with Apple that there are likely options -- both within Apple and external to it -- for replacement which didn't necessarily exist before. So, for the sake of argument, let's give Steve's eventual replacement the benefit of the doubt and say he'll be an effective leader of Apple.
The question ultimately comes down to whether the existing Apple customer base as well as the general public does two things:
1. Gets over Steve Jobs
2. Gives the new person a chance
Sadly, I don't think these are things we can afford to just assume and expect to happen. Almost certainly when Steve leaves (in a few weeks, a few months, or several years from now) Apple's stock is going to take a hit. How much and for how long, of course, is a question nobody can know right now. But it certainly is going to happen, just as certain as I am sitting here in front of my Mac mini, typing this on my wireless Logitech keyboard.
I wish Steve all the best, and hope he is able to fully recover and return permanently to Apple. Likewise, I'd love to see this thread go away, but I don't think this sort of thread will ever entirely go away because we all know, one day sooner or later, Steve will leave Apple, and when that happens, we're going to be right back where we started in this thread, only worse because then it'll be for real, and we're all of us going to be sitting here, to one extent or another, wondering what will happen next, and whether we can truly trust the judgment of the next guy.
Which brings up another point, actually, and that is the role of the person who comes after Steve. Steve has achieved a number of very incredible things, the very least of which is turning Apple around in the financial sense. Before Steve came back, Apple was rapidly loosing relevance. They had no clear strategy or vision for the future. Their OS was seriously legacy, badly in need of an overhaul, and nobody at the top in Apple's structure had the vision or capability to drive the company in a positive direction. Before Steve, they had a confusing, complex, and aimless product line. They had no killer products, and frankly were only able to tread water simply because of the fanatical devotion of many of us long-term customers. Before Steve, Apple was a near-laughingstock of a company; with no street cred, no traction, and no leadership role in the technology industry. Steve changed all of that, and rightfully deserves an immense amount of credit for all the results he's thus far achieved.
So, short of the Second Comming himself taking over for Steve, those are some pretty big shoes to fill, and anyone who might get the job is going to be, frankly, somewhat untested, untried, and usurping the footholds of success often described as "standing on the shoulders of giants". Again, Steve deserves our gratitude and thanks, but we've elevated him to such an extent, and placed him on such a high pedestal, that (in my opinion) I don't think anyone can come close, and so everyone who could conceivably come after will seem like a let-down.
It's not fair, not to them, not to Apple, not to Steve, and not even to ourselves.