SquareEnix already has remakes of I-IV on DS which are probably reasonably readily portable to iOS/Android; they've already released III and I on Android. You

SquareEnix already has remakes of I-IV on DS which are probably reasonably readily portable to iOS/Android; they've already released III and I on Android. You can probably expect to see II and IV on Android within a year if they continue to sell well, but probably not V or later until they're ported to a portable game system first. I know there were reports of preliminary work on V/VI for DS but nothing beyond that.