When Is: 2.21 Coming Out
If you mean — Linux kernel versions jumped from 2.6.x to 3.x, so 2.21 was never released.
If you meant — Blender 2.2x series is very old (early 2000s), and 2.21 would have been released around 2001–2002 if it existed. when is 2.21 coming out
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 — Linux kernel versions jumped from 2
If you mean — that was released in 2010. when is 2.21 coming out
