After Episode IX, I think that they should take at least five years before releasing X. Actually, I think that they should wait even longer, but I know that's not realistic. I also think that they should take a couple of years off after putting out the Obi-Wan movie.
On a side note, I watched Rogue One for the first time since December last night. I really enjoyed it, as I did before, and think that it expands on the Star Wars lore beautifully. I don't think that it's as entertaining as The Force Awakens, but it's got some incredible moments.