Square Enix has confirmed that Kingdom Hearts: Dream Drop Distance HD will be rendered in 1080p and will run at a smooth 60fps.
Square Enix made this announcement over on the official Kingdom Hearts Twitter page. They added a small excerpt of gameplay footage from E3 2016 that proves that the game is running at 1080p and 60fps.
Tetsuya Nomura confirmed that Kingdom Hearts: Dream Drop Distance HD is the first game in the series to run at 60fps. The game is a remake of the 3DS original and it looks bigger and prettier than ever before.
The video below also shows gameplay from Kingdom Hearts 0.2: Birth by Sleep–A Fragmentary Passage. Looking at the two games side-by-side, you can tell that 0.2 is running at 30fps. This is a sign that Kingdom Hearts 3 will also be 1080p/30fps since they are running on the same game engine.
Both Kingdom Hearts: Dream Drop Distance and Kingdom Hearts 0.2: Birth by Sleep–A Fragmentary Passage are a part of the Kingdom Hearts HD 2.8 Final Chapter Prologue collection. The game also includes Kingdom Hearts χ Back Cover which is full of cutscenes only. It will be out exclusively on the PS4 in December 2016.