Really.
That's because, for starters, 8k is overkill for 4-perf 35mm film.
Also, the vfx shots in TFA, which I'm assuming will make up a pretty sizable percentage of the movie, will not be rendered at anything higher than 4K except for the shots in that one IMAX scene.
When most of your movie is stuck at 4K to begin with, you're not going to gain much of anything by mastering it at a higher res.