I wonder if it will feel significant.
I can't remember being limited by the controller battery.
The runtime on a single charge is probably still going to be measured in weeks, and at that scale I feel like it doesn't really matter.
It's because they're basically already using user replaceable batteries, to the point I'm not sure what the SKU revision will actually do. My best guess is they won't be gluing the battery down any more? Otherwise there's not anything I can see they would need to change.