The WordPress Core Development team has published the WordPress 5.6 Field Guide. This is a good document to review as you prepare for the release of WordPress 5.6 in December.
This release includes the features that were released in versions 8.6 to 9.32 of the Gutenberg plugin. There are some significant improvements, but many of the new Block Editor features originally targeted for this release were deferred.
Here is a summary from the Field Guide of the highlights of this release.
As a user, you’ll see automatic updates for major core releases (opt-in), external authentication to the REST API via newly introduced Application Passwords, PHP 8 support, the latest and greatest features in the block editor, and a new AAA-ready default theme. As a developer, you’ll see 85 enhancements and feature requests, 201 bug fixes, and more! Of course, all those improvements mean code changes, which could in turn require you to make updates to your site, plugin, or theme.
WordPress 5,6 Field Guide