In reply to Peter.

https://make.wordpress.org/core/2019/02/08/wordpress-5-1-field-guide/

WordPress 5.1 includes the equivalent of the Gutenberg 4.8 plugin, but with some of the packages updated to fix some important bugs:

https://core.trac.wordpress.org/ticket/46137

Which version of Gutenberg will be included in 5.2 is dependent upon what the latest released version of the Gutenberg plugin is when the 5.2 beta starts. I think once the beta starts, the Gutenberg-related packages are not updated for the release unless a serious bug is found.