Well, this is how I see it. Take it for what it's worth.
They built WP7 on the old CE OS yet made it completely incompatible with existing WM6.5 which forced a lot of people like myself into the cold until we moved to WP7. Now, they are using the existing old tech NT kernel for the newer OS and somehow are going to make it so that many/most of the existing apps will still function. Similar to how older programs are still backwards compatible on our computers. these phones we use now are more sophisticated than the desktops we used less than 5-10 years ago.
So long as Microsoft continues to use and build on their existing OS's Kernel to create the next levels WP8,9,.......15, etc, I see no problem here. Perhaps it will go back to the way it was in the older days of CE, 2003,.....,6.5. Perhaps, I can see it finally getting to a point of total connectivity and cross platform compatibility where we'll see programs bought and labeled as being compatible with, Win(12 speculative) and it being capable of running on your tablet, Phone and desktop.
The only real issues I have with MS is how they've marketed and pushed these changes. There was no real reason to make WP7 incompatible with 6.5. If they were planning ahead to recreate the whole OS from scratch anyway. WP7, 7.5, 7.8, was just an unpublished stop gap measure. Why create a hardware platform that was going to be changed back to essentially what it was before aside from the actual chip sets. Ever since the introduction of WP7 from WM6.5, I see nothing but bad marketing and implementation. They really need to step up their game if they hope to come back to even a fraction of what they once were in mobile computing. No real marketing, constant major changes(as seen by the public at large) making what was bought today nearly useless tomorrow. This is more than a simple issue of advancing technology. It's poor planning and poor marketing in my eyes.
Reminds me how Commodore ran their show. they dominated and became lax and let everyone else pass them by. Where are they now?