We’re actually scraping the barrel on candidates to what could be the next Community Day Pokemon after Torchic Day and before Mudkip Day (June), so it may be sooner than we think.
I’m suspicious that it will be Earth Power for Gible Community Day as it’s an exceptionally powerful move, and Garchomp learns it via tutoring in the core games. Since Dragon Rush isn’t currently in the gamemaster file, it seems the most likely candidate. It would also surpass Groudon as a Ground-type attacker if it gets Earth Power.