Current devel version will be numbered 5.2.0 and it is planned to be released during 2018.

Previous devel, current stable, version was 5.1.x (released on November, 2017), see what was new in that release at:

• http://www.kamailio.org/wiki/features/new-in-5.1.x

This is a draft of new features added in devel version, manually updated, thus not always synchronized with what is new in source code repository.