I can see getting a teaser trailer released publicly this early if they are really trying to push Gladiator II as a big end of year event movie, like what Dune: Part Two was supposed to be last year and what Avatar: The Way of Water was the year before.
There might be a bit of trepidation surrounding it after Napoleon bombing, but I think this, just by nature of being baked in as a sequel to Gladiator, is going to have a lot more mainstream appeal and interest in it right off the bat once the general public becomes aware that it's coming.
Plus, don't all the kids care about ancient Rome now after some TikTok trend or something?