Also: sure, in 8 years the iPhone may be dead and Apple bankrupt, but (1) do you really think so? and (2) do you really need to plan that far in advance?
Regarding advantages to the software developer, having just one place where you distribute, and that place being controlled by Apple, isn't a good thing at all. It may mean that it's easier to start selling, but also that you have no negotiating power if and when your app becomes a success.
The stupid music companies managed to hand over the keys to their distribution to Steve Jobs, but they're not exactly happy about the fact that he now has so much control over their fate. Apple's great at creating consumer electronics that actually appeals to people, but they don't seem to be a very nice company to deal with as a business.
So it's looking pretty good so far, even if no phones are running it just yet heh.
7-8 years ago I used to develop mobile apps in both Palm OS (closed platform, just one vendor) and J2ME (open, widely adopted). Palm had the more attractive installed base back then, but as their fortunes changed, that investment is now worthless. Compare with J2ME, which kept growing thanks to support by most vendors.