Beta 4 is very likely to be the last test release before the full release of 0.9.9. The only thing left to do with it is, to document and test the migration path from WordPress installs.
There are two changes from Beta 3:
- Compatibility with the upcoming PHP 7.3 version.
- Fix for a minor bug which in a development environment caused JS errors, as there was an attempt to use non existing un-minified JS files.
You can download it here