To be fair we might not even get any new mythical Pokémon for gen 9 as it feels like your there drifting away from the idea of mythical Pokémon. Plus it feels like the vast majority of mythical Pokémon exist just to be tied to and sale Pokémon movies.I think we still have one or two more event Pokémon, those being the new Mythicals, that will be released after the DLC launches. Terapagos and the smaller version and Ogerpon and the other three Pokémon for Teal Mask seem more like new Legendaries similar to Kubfu/Urshifu and Calyrex and its Steeds. There is no Pokémon for Gen 9 that screams Mythical right now.
I mean heck most if not all mythical Pokémon could just be legendary Pokémon with seemingly the only difference being that mythical Pokémon are usually locked behind an event.