Episodes come out weekly on Disney XD at 9am on Saturdays. Yesterday was Episode 80 or the Ice Cave Episode wherein Lillie got an Ice Stone and Icium-Z(which is complete BS seeing as she doesn't have a Z-Ring yet. Lana at least got the basis for one prior to her getting Waterium-Z). Anyways, Episode 81 is next week(December 1st) with Ash and Royal Mask. Episode 82 and Steenee evolving into Tsareena is on December 8th. Faba is an Idiot(along with Episode 83) is December 15th, Mina and her Fairy Type Pokemon make their appearance in Episode 84 on December 22nd and the latest Ultra Beast Episode(not counting Necrozma) in Episode 85 is December 29th. Nothing has been announced past that for the English Dub from what I can tell and whether Disney XD will air the Episodes in that order, I have no idea.
Japanese Dub, meanwhile, just aired Episode 98 and have announced Episodes up to 102(aka Brock and Misty visiting Alola). Speaking of Episode 102, that might signal the end to the Japanese Season like Episodes 42/43 ended Season 20 of English Dub. Something tells me though that English Dub may end at Episode 85 seeing as future Episodes have yet to be announced and that would put it at 41 Episodes this Season so far(since Episode 64 was banned). Granted I suspect that the English Dub will go for another 5 weeks or 5 Episodes and finish the Season off with the Necrozma arc and start up Season 22 with the Pikachu Valley Episode. In doing so that would place Season 21 at 46 Episodes. Then again, I can't read Disney XD Executive minds so *shrugs*, you'll get more when I find out more lol.