I think Apple would restrict development requirements in the App Store to ban iOS apps created with a Non-Apple compiler on a Non-Apple platform just like they banned Adobe Flash and iOS apps made with Flash.
Not only that but Apple would sue anyone who made an environment to run iOS apps on a non-Apple operating system.
I kind of have a Love-Hate relationship with Apple because of that. I feel that iOS apps should be made on any platform and be allowed to run on any platform. Android is the complete opposite of iOS/Apple, any platform and any language can develop Android apps, you can choose more than just one store to buy apps from, and there is this Bluestack app http://bluestacks.com/ that runs Android apps on Windows and there is a beta for Mac OS X IIRC. Not only that but there is an Android for PC OS: http://www.android-x86.org/download
For now people want to develop for the App Store and they pay for the expensive machinery to get a piece of the action. If the Google Play Store ever becomes the trendy target market and Apple's position is threatened, I imagine they might consider opening up.