The rumor stems from the latest PlayStation Studios banner update.
In particular, Sony changed the webpage for PlayStation Studios to show Demon's Souls, updated designs for Aloy and Gran Turismo, as well as a new MLB player.
Finally, Sony removed Concrete Genie in favor of Death Stranding.
Of course, it is worth noting that Sony also owns the Death Stranding IP, and the console manufacturer has stated before that non-Sony studios will get the PS Studios branding if Sony is producing the game.
With zero precedence, it's worth keeping an eye on Sony and Kojima Productions, just in case.