According to the report, Kojima is in the process of founding a new development studio, and is already in talks with Sony about his new studio's first game.
This seems to be the final movement in the long breakup between Kojima and Konami. The cracks began to show in March, when Konami was restructured and the Kojima Productions name and logo were removed from promotional materials for Metal Gear Solid 5: The Phantom Pain. Konami soon after canceled Kojima's partnership with Guillermo del Toro on Silent Hills, and formally dissolved Kojima Productions. Earlier this month, Konami did not allow Kojima to attend The Game Awards, where The Phantom Pain was nominated and won the award for Best Action/Adventure Game.
Previous reports suggested that Kojima had been let go by Konami, and that he was simply waiting for the non-compete clause of his contract to expire in December to make his next move. While the rumor was flatly denied by Konami, the timing of this latest report, if true, lines up with what was previously reported.