It's a really exciting new update and nearly a major update due to all of these upcoming improvements.
There is a lot of new stuff coming up in WordPress 5.5 like

Lazy loading for images
Block editor improvements
Better Inline Imaging Editing
Block patterns section templates
(Mobile) device previews
Background Block Colors
Block navigation
New measurements
XML site map
Auto updates for theme and plugins
Better manual theme and plugin updates

Especially lazy loading and the new ability to upload plugin packages when a already is already installed is amazing. No more need to uninstall a premium plugin before being able to upload an updated package.

I've written an article with details to all these new things in WordPress 5.5:
https://wp-staging.com/wordpress-5-5-update-of-the-year-exciting-new-features-improvements-bug-fixes

Cheers
René