Beg to ILCA, they’re developing Brilliant Diamond & Shining Pearl, not Game Freak.
We just have to hope that Brilliant Diamond & Shining Pearl will be compatible with Sword & Shield. Hopefully Game Freak will release Version 1.4 for SwSh with compatibility with any Pokémon and move set changes BDSP brings that SwSh doesn’t currently have. If not we might have a repeat of the Let’s Go meta from last gen, or even just stick with the current Gen 4 metas, depending on how close BDSP sticks to the originals (and from what I’ve heard, the remakes are supposed to remain pretty faithful to the originals, so even if BDSP and SwSh are compatible, it’s unlikely Electivire will get a new move it doesn’t have in any other game). I guess we’ll have to see what ILCA and Game Freak choose to do in Late 2021.