Here is a message from SNK producer Yasuyuki Oda on the delay:
There are many fans who are anticipating the release of The King of Fighters XV in 2021, however at this point in time, we unfortunately have to announce that The King of Fighters XV will now be launching within the 1st quarter of 2022.
The development timeline we set out to reach in the beginning has been affected by the ever-still rising cases of COVID-19 within Japan. We have made the ultimate decision in the end that the product’s quality must come first, and so with that decision comes an altered release window.
We sincerely ask for your kind patience and understanding as our development teams continue to work hard on The King of Fighters XV as we draw closer to its release.
Release platforms for The King of Fighters XV have yet to be announced.