The RC3.x series has been so stable that we are re-versioning it to 1.x series and the RC4.x to the 2.x series. What this translates to is that RC3.06 will become 1.3.X and the RC4 candidate will be numbered as 2.0.X due to all the major core changes that's been performed. As each version is enhanced/bug fixed, we'll have 1.x.x and 2.x.x to better reflect changes.
With the version changes, the 1.3.x series will go into viability mode (bug and security fixes only) and the 2.x.x series will become the future development platform for the core team
We hope you like the new numbering scheme and the changes coming down the pipe.