[HardyLeung]

I don't think this is entirely correct. If you write in Native (C/C++) then true, it won't run on WP7. But if you write in C#/Xaml you could have targeted your app to WP7 and I believe it will run on both WP7 and WP8 -- of course this will preclude you from using whatever now hardware capabilities in WP8 only.

I think the Native C/C++ is the right move though. The "easy to port to IOS/Android" point is important, and I think going forward that would/should be the model for web development, unless Webapp is sufficient for your purpose, or that you're willing to develop your app in 3 languages (ObjC, Java, C/C#).

That said, I'm sad that my (otherwise very nice) Lumia 800 is getting the WP6.5 treatment.