This will increase engines from 6 to 9. SpaceX will also increase fuel to about 300 tons. This will enable a larger Starship and Superheavy to launch 220 tons to orbit instead of 150 tons.
On December 17th, the Elon confirmed a tweet from three months ago.
The SpaceX Starship would be stretched about 5-6 meters with larger fuel tanks.
The full refueling of Starship in orbit would drop from 8-9 launches down to 7.
The ship is just begging for three more vacuum engines to be added. Tanks will stretch for more propellant load.— Elon Musk (@elonmusk) December 18, 2021