The original hope was for it to be tied to the Olympics but it had problems even before the COVID hit.
The summer 2018 anime series Free! -Dive to the Future- brought out its compilation film back in 2019 and had set plans for an original film as part of summer 2020 previously that would tie nicely into the Olympics.
That hit some snags back in the fall of 2019 as the official site talks about “various circumstances” that have caused the film to be delayed.