The answer is here:
https://launchpad.net/unity8-desktop-session
Subscribe to the bug mail if you want to keep up to date. Installing this will require some aptitude on developing for Ubuntu.
I contacted the head of the team some time ago, and he was just getting things together. Considering though their focus is on the phone; hardly any push from the development team at Canonical has happened thus far. As far as I understand from speaking to community developers on IRC; the Tablet implementation will be the next official focus for development, and they will be holding a design conference for that sometime in the near future (It could have already happened; I just have not heard about it. If someone could confirm, please comment.) To which then after will a Desktop design session be held some time around 15.04 I believe.
edit:
Just download 15.04 from daily images; it should have the most recent version of the desktop.