Pokebank has now been updated so you can now use Sun and Moon with it. You can also transfer Pokemon from Pokemon X, Y, Omega Ruby and Alpha Sapphire to Sun and Moon, as well as use Poke Transporter to transfer Pokémon from the Virtual Console releases of Pokémon Red, Blue, and Yellow to Sun and Moon - but it's all a one-way trip, remember.
Also Pokemon Sun & Moon players who use Pokemon Bank will receive the
Mewnium Z until
October 2nd 2017. This will allow you to perform the
Genesis Supernova Z-move with a Mew that knows Psychic.