this was said about a possible Android version too, not too long ago, but guess what: you pulled it off.
I remember Marc said that WP7 did not support for writing in native code c++, but as things stand now, W8 and WP8 support c++.
As Microsoft said, by allowing for coding in c++, we will see much, much more apps developed for iOS and Android, have an easy port to WP8 as well. I'm only saying.
It would be sad if your great game won't be available for W8, as it will likely have a greater market share then iOS and Android combined.
I am using W8 on the desktop as well as on an Acer W500 and the tablet works incredible good with the new Metro UI.
I can't see why it can't be done, other then the lack of interest in the new W8.
I'd like to hear the opinions of the developers.