Hello,
with the creation of branch 5.2 done this morning, the master branch is from now on open for adding new features, to be part of future release series v5.3.x.
Any bug fix committed to master that applies to 5.2.x or older stable branches should be backported as usual with git cherry-pick to appropriate branches like 5.2 or 5.1.
Expect that v5.2.0 will be released in about 2-3 weeks from now.
Based on the workflow used during the past years, the next future release v5.3.0 should be out after another 8-10 months of development, plus 1-2 months of testing, so sometime in the summer or autumn of 2019.
Cheers, Daniel