An update to the Pokémon Bank Service has been revealed as planned for January 2017. Pokémon Bank is a Nintendo 3DS App which allows players to move Pokémon between games, the new update will facilitate this for Pokémon Sun and Moon, as well as the Virtual Console versions of Red, Blue and Yellow.
This information was found as part of the video description for a video promoting the service on the Japanese Pokémon YouTube Channel. A new trailer for Sun and Moon is expecting later this afternoon.
Originally, the update had been expected to arrive along side Sun and Moon in November, but a short delay is nothing to worry about given how many new Pokémon there will be the discover when the new games arrive.