Windows Phone 8, codenamed Apollo, will be based on the Windows 8 kernel and not on Windows CE as are current versions. This will not impact app compatibility: Microsoft expects to have over 100,000 Windows Phone 7.5-compatible apps available by the time WP8 launches, and they will all work fine on this new OS.
That’s interesting and in reading his post it sounds more and more like Windows Phone 8 will be very similar to Windows 8. That is: it will be a sibling to Windows instead of a cousin to Windows.
I am not sure if this will be good or bad, but if they can pull it off while maintaining app compatibility (even while adding more screen resolutions) it should be a win.