I dunno Kev. I really think Apple isn't stupid enough to lock off their Desktop apps. Sure they're building an App store, but it's been clear in the Dev documents that it's meant to supplement, not replace traditional methods of installing applications.
iPhone, it makes sense for them, as it is their platform, and the App Store is the major draw for many people. Mac OS.. they'd be killing themselves if they locked the OS down, and not even Apple is that foolish.