Indeed apps may require a re-compile, but I suspect this may be familiar territory for QT apps targeting multiple devices. Though it presents a quick route for QT developers to capitalize on the installed base of both OSs.
The bottom line is this: there's a clear trend towards application independence from language and OS, and within the next few years (as little as 5), it won't matter if you're running Android, MeeGo, BBOS, Win7, Ubuntu, etc as most applications will run just as well on any platform without the need to write in a particular language or cross-compile.
What's more is that as these apps can be web delivered: there will be no need to even install ushering a new wave as software as a service, but with the sophistication and speed of traditional apps!
At that point, the phone/tablet/pc becomes a true appliance, only specs and brand and build-quality will matter to consumers (like all appliances), and platform zealotry will become a thing of the past.