The question is how. Possibly a new enhanced version of Pokémon Bank will be released for the Nintendo Switch, and transferring would go from the Bank account on a 3DS to a Bank account on Switch, and then from the Switch Bank to SW/SH. There could be limitations set, one box at a time, requiring the Gen 7 "white seal", etc, but I can see it happening. Please, please, GF, don't do what you did in Gen 3 again...