It seems that the release note list (not the intro) is the one for release 3.
Oh, that must be why I can’t find any info about the “Beta of new IDE Communication protocol” 
There are no difference in release notes except for summary
That link has been updated with the appropriate notes.
Very Cool! Thanks Paul.
2016r4 Release Notes (in Announcement, on Web): Windows HiDPI support is finalized.
Documentation (in the included Documentation-folder of 2016r4), File ‘DesktopHiDPISupport.pdf’ (Modification Date: 02.12.2016): “HiDPI support on Windows is considered Beta at this time.”
It seems we can make our own choice to decide whether HiDPI for Windows is still Beta or not 
(or maybe it’s simply a finalized Beta)