the htc one m8 did it with 8.1, and now xiaomi with w10, if you take a good look, vast majority of phones, android or wp, use QUALCOMM chips, its not like intel would make a special cpu for every mac or pc or Linux server, it somebody gets ahold of a w10 iso or rom or whatever that may be, I'm sure it could be installed on almost any "android" phone with compatible hardware, that means any sd200-400-800 etc
its just that Microsoft have not provided that option, and now is just not worth it anymore, before w10m, having the option to install lets say wp8 or 8.1 on your android phone could potentially mean the end of lag and dead batteries if android's complexity was giving you a hard time, but not anymore, w10m is just as bad in that regard, or kind of worst since the OS is not open and meant to be fine tuned by the user, so you're at the mercy of "bug fixing" updates from Microsoft