Alegria
Alegria ♪ Caca0ch0c0lat
Towns Folk
I saw today there was an update, so I searched why, several sources told me the same as here:
http://www.perfectly-nintendo.com/pokemon-ultra-sun-ultra-moon-software-updates/
the official website doesn't tell anything yet, however
https://www.nintendo.co.uk/Support/Nintendo-3DS-2DS/Game-Updates/Pokemon-Ultra-Sun-and-Pokemon-Ultra-Moon/Software-update-December-13th-2017/Software-update-December-13th-2017-1319238.html
so basically it would just be minor bug fixes on moves during competitive battle.
http://www.perfectly-nintendo.com/pokemon-ultra-sun-ultra-moon-software-updates/
the official website doesn't tell anything yet, however
https://www.nintendo.co.uk/Support/Nintendo-3DS-2DS/Game-Updates/Pokemon-Ultra-Sun-and-Pokemon-Ultra-Moon/Software-update-December-13th-2017/Software-update-December-13th-2017-1319238.html
so basically it would just be minor bug fixes on moves during competitive battle.