One thing that matte seat backs MIGHT impact is the usability of suction cup mounts on the seats. Those of us with small children often use suction cup mounts to stick an iPad onto the back of the first row seating on long trips. This allows kids to watch movies on long drives without breaking their necks, and works wonderfully with the glossy backs. Of course, in most other cars you can just use a headrest mount, but Tesla's seat design precludes that.
With the matte backs, does that solution still work? Because there aren't many solutions that would work in the X, so it would be sad to lose the one that is known to work well. In our case, the kids will likely not care about this by the time we're ready for another car (they'll be older). But just getting an X today, if suction cups are not workable due to the matte seatbacks, I guess I'd be resorting to an adhesive and magnets.