Square Enix has revealed its schedule for the forthcoming Gamescom in Cologne, which includes an English version of Dragon Quest IV: Chapters of the Chosen. So it looks like this epic RPG will have a western release on iOS sometimes in the future.
Dragon Quest IV was originally released on the NES and then ported to PlayStation and Nintendo DS with differences respectively. The iOS version will be based on the DS remake and presumably with some changes.
Nothing else is known about the English iOS version. Nor words on the release date. But more info will certainly roll out in next month at the Gamescom.