The battery capacity of the Galaxy S21 Ultra has been revealed, and it seems that Samsung is happy with the 5,000 mAh battery from the S20 Ultra. In fact, only the Plus model is in the frame to receive a larger battery of the S21 series.
https://www.notebookcheck.net/The-Samsung-Galaxy-S21-Ultra-will-have-the-same-battery-as-the-S20-Ultra-only-the-Plus-model-is-in-line-for-a-larger-battery.494473.0.html