I just don’t see how an announcement of only the SE (and the prequels and TFA/RO) in 4k would be met with any other response than “who cares?”
Disney should be smart enough to know that this is it for Star Wars on physical media and that they might as well put together the definitive collection for all time.
If they want to do it this year, they can just leave a little extra space with a cardboard placeholder for where Episode IX will eventually go.