A beta build of version 4.5 is now available on the beta branch on Steam. This updates the engine to the latest Newton 3.14. Versions 4.5 and 5 beta are now compiling side-by-side with the same source code. Because of major engine changes in version 5, some bugs may need to be resolved before the final release. Some preliminary information on updating C++ projects can be found in this thread.
Version 4.5 is planned to include official support for VR (both Vive and Oculus) and a new improved vehicle system.