If any developer needs to store code of new features in the repository, he/she has to use personal branches (or temporary branches in tmp/ when many developers work on the same code). After unfreeze, these branches can be merged in the master branch. Therefore, what is now in master branch will be the code base for v4.0.0, after release the config file you build now will just work.
For 1-2 months from now on, the main focus with the master branch is testing. The v4.0.0 will be out after mid of February, 2013, exact date to be set later based on the results during testing phase.
There were many additions, so any kind of help testing is very appreciated. Fortunately the core and most of the very used classic modules were not changed much, ensuring good stability. But there are old very used pieces such as usrloc/registrar that got touched as well, so try to test as much as possible the components you are using in your configs.
Many brand new additions should give enough reasons to look at v4.0.0:
- no more duplicated modules – Kamailio-SER integration has been completed
- websockets support – make calls between web browsers directly through Kamailio
- IMS modules (about 10) are part of the distribution
- SIP Outbound extension
- embedded provisioning interface
- … for more see the draft of what is new in devel version