Thekla Inc, developers of The Witness, has announced that there will be an upcoming patch for the game so as to support the PS4 Pro.
The patch will add a 4K mode with upscaled HD render at 60fps and native 4K UI, with the team also considering 1440p before upscaling. For those with a 1080p display the game will render at 1080p instead of the current 900p. Antialiasing quality has also been increased from 2x to 4x MSAA. In addition to all of this, Thekla are considering HDR support, although this, amongst many other decisions, isn't finalised. Full details on the plans can be found on their official site.