VirtualBox 5.0 will be a new major release. Here is an incomplete list of changes since VirtualBox 5.0 Beta 4:
•GUI: NLS fixes. NLS strings are now frozen.
•GUI: Improved HiDPI support for Windows host, icons/size-hint adjustments.
•GUI: Use fast scaling mechanism for integer scale-factors (s. a. here).
•Separate UI/VM: fixed completely broken re-attaching to a headless VM.
•Drag and drop: fixed hang when reporting host errors such as inaccessible (locked) files.
•PCNet: OpenStep fix (bug #10545)
•Host-only networking: an attempt to fix some VERR_SUPDRV_COMPONENT_NOT_FOUND problems
•NAT: Don't forcibly reset/drop all connections when link goes down
•AHCI: fixed a possible hand during VM shutdown
•Audio: fix audio output if the default output device changes, before this fix it would always stream to the output device being the default when the VM was started
•VBoxSVC: don't keep the support driver permanently open
•VBoxManage addencpassword: read the command line from the console or from a file
•vbox-img: added resize command
•X11 Additions: fix for X.org servers with RandR 1.1