First and fore most: there are only 2 mythicals this gen and as we know mythicals are used for movies promotion and movie distribution.
We have Magearna and Marshadow.
Magearna was already used for gen 7 promo this summer (qr code is already avaible)
Marshadow is for next summer
And thats it the dont have anything more

Well TECHNICALLY there's one more mon: Eternal Floette with the most powerful Fairy move Light Of Ruin. Yes AZ Floette is in SM aswell although i doubt it it will be used in SM because why would they since there's no AZ or anything

I can see another gen 7 game next year with some new forme for Marshadow and gen 8 in 2018

Question what game though? GF said they want to surprise people and Eclipse/SM2 is way too obvious since tons of people talk about it already (plus SM has less loose ends than gen 6 and even 5). Kanto re-remkes wouldnt make sense a year after the 20th annivesary and Sinnoh remakes seem to early