Blackberry and Android are the only major mobile platforms that can use Flash. Well, not including Win8.1/RT. Android officially dropped Flash, but you can still download an older version as a Firefox plugin, without even rooting. I have it on my stock Nexus 7 (2013).
Blackberry ports it to a mobile version, themselves. Which any platform could still do if they wanted.
I wonder if WP9, or whatever the phone version of Threshold will be called, will have the desktop browser or not (which would mean Flash support if it did.)