Mageia 6 Development Snapshot 1, which was originally supposed to released back in 2015, has finally made it out onto the mirrors. The entire Mageia 6 release schedule has been in a hiatus due to this belated Dev1 ISO. Per the Wiki page, "Estimated dates for the future development releases and final public release will be announced as soon as the first development snapshot has been released. At that time we should hopefully be already way into the stabilization phase and ready to iron out the last issues."
I have yet to see any official Mageia 6 Dev1 release announcement hit the wire, but interested users can now find it via the Mageia FTP mirrors. The Mageia 6 release notes are still a work in progress.