Mark Hamill has shot extensively for Episode 9 (extensively with respect to how underused he was in 7 and 8). His relationship with Fallout Boy is being featured as more of an arc this time, a step up from the cheap cringe montage we got in Episode 8. Mark's shot a lot of dialogue, and I expect a good amount of quality character building for Skywalker and Ben Solo as a result of these shoots.
I don't know how much will make it into the movie. There are a bunch of new characters and they still need to keep Finn and Rey front and center. But at the very least, Luke will get his proper sendoff-- albeit from the grave.
Better than nothing.