Well Yoda hit Luke on the forhead with his cane in TLJ signifying that force ghosts are some sort of physical beings, so Luke could come back and influence anything now…
I honestly could care less about episode IX. Rey’s character/story is the only pary I’m mildly interested in. I wish they kept Rogue One’s characters alive. I would rather of seen their alternate view to the OT. That’s what made Shadows of the Empire so intriguing.