Here is what the official blog says:
This is an important milestone as we progress toward the WordPress 5.2 release date. “Release Candidate” means that the new version is ready for release, but with millions of users and thousands of plugins and themes, it’s possible something was missed. WordPress 5.2 is scheduled to be released on Tuesday, May 7, but we need your help to get there—if you haven’t tried 5.2 yet, now is the time!
What’s in WordPress 5.2?
Continuing with the theme from the last release, WordPress 5.2 gives you even more robust tools for identifying and fixing configuration issues and fatal errors. Whether you are a developer helping clients or you manage your site solo, these tools can help get you the right information when you need it.
The Site Health Check and PHP Error Protection tools have brand new features, giving you peace of mind if you discover any issues with plugins or themes on your site. There are also updates to the icons available in your dashboard, fresh accessibility considerations for anyone using assistive technologies and more.
Plugin and Theme Developers
Please test your plugins and themes against WordPress 5.2 and update the Tested up to version in the readme to 5.2. If you find compatibility problems, please be sure to post to the support forums so we can figure those out before the final release.
The WordPress 5.2 Field Guide has also been published, which goes into the details of the major changes.
How to Help
Do you speak a language other than English? Help us translate WordPress into more than 100 languages! This release also marks the hard string freeze point of the 5.2 release schedule.
If you think you’ve found a bug, you can post to the Alpha/Beta area in the support forums. We’d love to hear from you! If you’re comfortable writing a reproducible bug report, file one on WordPress Trac, where you can also find a list of known bugs.
Howdy, RC 1!
With tools this interesting,
I can hardly wait.