I see no reason whatsoever why a new Star Trek film would need to take place in the Kelvin timeline. As much as I enjoyed those films, they only existed because Paramount wanted to make films in their own Trek universe. But nobody knew that a bunch of shows would later be produced in the allegedly 'prime' universe. Now with the merger, shows like Discovery, Picard, Section 31, Lower Decks, Prodigy, _______ (fill in the blank), etc. are the focus now. Setting a new movie in the Kelvinverse or any other alternate universe would just be needlessly convoluted. Plus, genre movies these days tend not to stay in any one continuity for very long.
The Kelvinverse had three films, and they rejuvenated interest in Star Trek. They did their job, and there's really nothing more we need from them.