Because 5.x is already getting meaty with updates that are under risk of becoming stale and are already hard to keep up to date, we have decided to start merging 5.x work into the master branch.
Prior to doing this, we will create a 4.x branch, which will receive all pending work that is on the course of being developed and delivered for 4.x. We will release a future 4.22.0 from this branch. Any bugs or additional work that needs to be published in a 4.x release will be merged into this new 4.x branch along with master. We will add the same branch protection rules to the 4.x branch as on master to insure it is stable.
This means that every contribution to 4.x will need two PRs - one merged into 4.x and one merged into master. This can be a bit of a hassle, but we will make an effort to make this interim period as short as possible.