Quoted By:
Reminder for where the pokedex ended before their respective mythicals in previous gens
>gen 1 right after mewtwo, the final boss
>gen 2 right after the cover legendaries
>gen 3 right after rayquaza, the third legendary
>gen 4 right after Cresselia for some reason, regional ends at palkia for dp and giratina for platinum
>gen 5 right after kyurem, the third legendary
>gen 6 right after zygarde, the cucked third legendary
>gen 7 right after necrozma in both SM and USM for alola dex
So yes, eternatus is the final pokemon in the ingame dex we will see until the datamine
