-3.10 will be released this weekend, eventually monday.
Code in repository is always in **release candidate stage** for next version. It's usable (because authors use it :-) ), but not all features have been extensively tested. After bugs targeted nextrelease are fixed, and it's proven that no standard features were broken in the process, it will be uploaded to CTAN.
After that, some of the bugs targeted futurerelease will be moved to nextrelease and the process will go on. We will consider odd numbered versions somewhat more unstable and containing experimental features, while even-numbered versions will contain mostly bug fixes.