Tesla would most likely release a sw update to unlock the capacity for free, as well as unlock faster supercharging rates as well, after they collect more real-world performance data. Maybe in a year or so. That was how they did for Model 3 and early 2020 Model Y. If I'm not mistaken, this would be Model Y LR battery "version 3". Tesla clearly doesn't follow the 2 year or 3 year refresh cycles, they just update whenever it's most convenient. It's great, but it does mean we are going to be testing for Tesla as they collect their new battery chemistry's real-world performance data.
I'd actually be okay with the capacity locked as extra buffer. A bit more top buffer means you could super charge to 100% more quickly, without worries of degradation. A bit more bottom buffer means you have more range safety and more "zero-mile" range. And you can do more frequent deep discharges without worries of degradation. I remember the old Model S 60D was basically a capacity limited 75D, and had the same advantages (plus lower price). Let's say you're on a long road trip, mid day: if you typically charge 30 mins per supercharger session 15% to 75% (60% charge), you can now safely do 10% to 80% in the same 30 min stop because of the extra buffer, which makes your trip faster overall, without actually paying to unlock the full capacity.