My guess would be that if Universal and Comcast are looking to the idea of having a new park open alongside the island for 2025, it could be as part of an agreement as part of the "Entertainment" for the area post-World's Fair, to keep that area alive and bustling in some kind of manner (separate from the actual WF, but on the island).
They have toyed with expanding outside of the Osaka park, with Okinawa once considered for a second gate in Japan. And with Singapore expanding it's initial park and Beijing likely to get two more parks (one dry, one water), it would make sense to see if Comcast wants to have another piece of the Japanese pie.