There will be almost no reveals about the game through the year and the next detailed info disclosure will come at the end of 2021 alongside the beginning of the promotional campaign before the launch.
While this is mostly personal speculation, this tells me that the next big reveal will be at Granblue Fantasy Fes, which is likely to be in December 2021.
The part 2 of the battle pass will come in early February, while chapters 46-50 of the main quest will come in late February. The music track for the final boss in episode 50 has been especially composed for the game by Tsutomu Narita. It’ll be an actual song with vocals.
Last, but not least, the fifth character of the second character pass will be revealed during Granblue Fantasy’s 7th-anniversary livestream in early March.
Incidentally, Fukuhara-san expressed satisfaction for the success of the game, also mentioning that thanks to the ongoing nature of fighting game, there are still many shipments.