Ultra Sun and Ultra Moon are entering new territory by introducing (at least) two new Pokemon mid-generation.
Not much is known at the moment but UB Burst and UB Assembly will be introduced in the upcoming Ultra Sun and Ultra Moon games, releasing November 2017. As well as the two new Pokemon, new forms will be released including Dusk form Lycanroc, Dusk Mane Necrozma and Dawn Wings Necrozma.
A preview of the new Pokemon and forms can be seen in the video below:
vBulletin Message