There are a few things going on:
- The 1.2 RC process has taken an unusually long time—this happens some times
- We wanted 1.3-alpha out so that people can start testing the multithreading work early
Given the amount of time it can take to get through the RC process, we need to move to a model where we are concurrently working on stabilizing one release while also working on features for the next release, so this will become the norm, except that there will not usually be alpha releases. In this case, 1.2.0 final will be released around the same time as we feature freeze 1.3 and create its release branch.