There is already currently 898 Pokémon, not counting Dynamax, Primal Reversions and Mega Evolutions, they didn't put it in Sword and Shield because there is to many. It wouldn't surprise me if they remove the National Dex all together or make it a future update or DLC as they steadily add more Pokémon. I'm ok with the National Dex being gone.
There is already currently 898 Pokémon, not counting Dynamax, Primal Reversions and Mega Evolutions,
