XNA actually makes for an interesting case here: it's so cross-platform that it's already missing a lot of the complicated stuff, which makes it a lot more likely that it can be replaced with something that can run on even more platforms.

The real question is just how they handle things and whether a suitable replacement can be found, or put together (project like OpenTK, Tao, SharpDX, SlimDX, and so on are the best bet there). Those both will take a bit of poking around or some info from their devs. 

In general, it would be a great chance and probably pretty interesting for everyone involved, but some more research certainly needs done.