The query "when is 2.21 coming out" is ambiguous without additional context, as "2.21" could refer to a software version, game update, app release, or other numbered release.
If you mean — no such version exists; the game is on 1.20+ (as of 2025). when is 2.21 coming out
If you mean — that was released in 2010. The query "when is 2