Tetris Best 3
From Hard Drop - Tetris Wiki
||This game is unreleased.
When the game is released, its page will be more complete.
||This game contains ideas for the Tetris Guideline 2.
If TTC uses this in the future, this may be the reference implementation.
Tetris Best 3 (TBIII) will be a future remix of Tetris Best 2. Anyone may be the creator, as the credits for Tetris Best 2 show that if you can improve Tetris Best 2, remix it into Tetris Best 3.
Its source code may be similar to Tetris Best 2. Some bugs may also be fixed. Other improvements will also be made, but it is unknown what they really are.
Creator may not like TBIII abbreviation though.