This trailer doesn't just show you what Final Fantasy IV looks like on iOS, it shows you the future. Or the past, given your perspective. The end of the trailer teases an iOS version of Final Fantasy V, "and more."
There's no timeline for the release of Final Fantasy V. It will likely be based on the original 2D version as seen on the Super Famicom and PlayStation, as, unlike FF4, there is no polygonal DS remake from which to work.