The earliest this project could have started was 2018, after they made Dragon Ball FighterZ. Before that, ArcSys on no one’s radar. The code that Tokon is definitely, without a shadow of a doubt built on debuted in Strive in beta form approximately 1 year ago, meaning that the project was probably not in ArcSys’ hands until after Strive launched, in 2021, at the absolute earliest. Sony had limited partnership arrangements with ArcSys at this point already, with PlayStation themed color palettes for characters in the game. But 2021 is also still likely to be too early, because Dragon Ball was still getting considerable attention, and GranBlue had just launched fresh into a world where it needed to be reworked for rollback immediately, because the market demanded it, eventually resulting in GranBlue Fantasy Versus Rising. So my best bet is that it started development in 2022.