From what I've been reading, Windows Phone 7 apps will run on Windows Phone 8, but not vice-versa. The thing to keep in mind is that you need to follow the app guidelines or your app won't get in the store.

>So, I'm downloading the Windows Phone SDK 7. Don't ask why.
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>I don't know.
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>How different is developing for 7 and 8?
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>Is there any way to know until it's released?
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>I don't really want to learn something that's only going to be relevant for another two minutes.
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>Which is why I should probably continue ignoring Microsoft.
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>But if anyone can sort of explain how the the process of developing a Windows Phone 8 app changes from the process of developing a Windows Phone 7 app that'd be worth a start.