iTunes has basically become "Stuff-that-can-be-synched-to-an-iPhone Manager." It could be broken down with little effort—Quicktime Player would get the movie/TV store; iPhoto would get the menu for synching photos; Software Update would get the App Store (and hopefully make it a Mac App Store in the process, because that's really not that much more work), and a new "iDentity" app would be created to handle all the other crap (because I use Gmail's web interface, not Mail.app, but want my Notes synced anyway, goshdarnit. Or they could just make a free reduced-capability version of MobileMe.)
The only thing that's stopping them from doing this is that, right now, you only need to download one thing in order to use an iPod or iPhone on Windows, and that one thing is completely owned as part of the Apple experience. After the conversion, you'd need quite a few more apps, some of which, due to just working through APIs, could usurped by badly-written, no-UX-consideration-given preinstallware that would give Apple a bad name (I can just imagine the "Dell App Store client"—oh, how Apple would rage at that.)
Apple would not design iTunes like this, if not for the need to deliver it on Windows. It breaks many of its own design rules.
The saddest part for me is seeing the open source desktops head down the same path when this could be a key differentiator for them. Like Apple they bundle a full working desktop with apps that can work together and build on the same libraries. But they don't.
Instead the future appears to be continuing with the totally inappropriate iTunes clone but switching to one that comes with it's on Mono VM and is becoming an independent development platform. It's latest feature is built in photo management! When I read that it was one of those satire is dead moments.
The only thing that's stopping them from doing this is that, right now, you only need to download one thing in order to use an iPod or iPhone on Windows, and that one thing is completely owned as part of the Apple experience. After the conversion, you'd need quite a few more apps, some of which, due to just working through APIs, could usurped by badly-written, no-UX-consideration-given preinstallware that would give Apple a bad name (I can just imagine the "Dell App Store client"—oh, how Apple would rage at that.)