We just pushed VirtualBox 5.0.0 into Debian Experimental. It should land up on your mirrors very soon.
Since this is a major release, we are looking for some testing and feedback. If you use VBox, or have your business depend on it, please give it a test. For details about what is new in 5.x, please check out the [release announcement](http://www.oracle.com/corporate/pressrelease/oracle-vm- virtualbox-5-070915.html)