In Japan, Final Fantasy XIII is on iOS, so is Dragon Quest X. Bet you didn't know that?
Granted it runs through Square-Enix's streaming service but still.
In fact a big part of the appeal of porting FFVIIR to Switch is likely that Square-Enix will easily then be able to port that version to iOS/Android. A huge percentage of Square-Enix's profit now comes from mobile, like it or not.
Mobile chips will continue to get better and better too, in 2-3 years, yeah you'll probably have 10nm mobile chips that can run even PS4 ports.