It's true that I can imagine a lot of future Ben Solo/Kylo Ren content is going to have to come in books and comics, especially in regards to his family, and that's great, but if Adam Driver is up for playing the character again along with Andy Serkis and expand the Ben/Snoke relationship further, I'd be up for seeing it in a movie. Besides which there's a good chance Mark might change his mind about playing Luke again, especially if it's a meatier role in a single movie (plus I suspect it's inevitable he'll be in IX as a Force Ghost anyway).