So you would suggest to create a branch 3.9 and rename the master to 4.0. The main goal of version 4.0 is to remove Java 5 and 6 and to assemble the distribution packages with Java7. All other features like DI, Buildsystem, etc. is for Minor-Versions of 4.x?
Sounds like a plan. I like small steps / small releases. But we should reduce the amount of bugs with testing. Bugs force us to provide bugfix releases instead of developing new features.
I'm still in hope that we follow the principles of the test pyramid of Martin Fowler after the move to a newer build system.