It cannot come to iOS until Apple allows Gecko to come over. It may happen eventually if Apple ever loosens up more on what engine is allowed besides Safari.
I can't see it helping much unfortunately in bringing more over, since Firefox desktop isn't that big either.
Firefox on Android would be perfect for me, if I could ever figure out why Firefox randomly freezes using the Google search fixer addon from time to time, and if Firefox would ever get tablet support (tabs).