WordPress 4.3 Release Candidate is now available! Release Candidate simply means it is a version which WordPress believes is ready for official launch, but there many still be compatibility issues with some software. Therefore people are encouraged to test 4.3 RC in order to find any remaining bugs before the official launch.
The official launch for WordPress 4.3 is aimed for 18th August 2015.
As always if you would like to read more have a look at the official WordPress blog post.