In a statement provided to VideoGamer.com last night, Square Enix explained that it is "still optimizing the game, and our target is 1080p at a minimum of 30fps. Anything beyond that is a bonus."
The statement is similar to the one made by Square in the run up to 2014's Tomb Raider: Definitive Edition, where it said that its goal was to deliver "the core Tomb Raider gameplay at native 1080p and running at 30fps". "Anything beyond 30fps for this version is gravy," it added.
In that instance, the PS4 version actually ran at 60fps, twice as fast as the 30fps achieved by the Xbox One version. It was also developed by Nixxes, the Dutch studio who has teamed up with Crystal Dynamics once again for the PS4 version of Rise of the Tomb Raider.