I'm watching the gameplay clips that have been shown, and to be honest, the graphics *in game* during battles are not as impressive.
They could "cheat" and use MP4 video for "story" sequences taken from the PS4 version and then cut to lower quality models for in-game battles. Just my two cents. That is basically how they used to do things back in the day anyway. I think that would make a port much, much easier.
540p for the portable mode, 720p for TV play.