DRI3 (also known as "DRI3000") is an update to the Direct Rendering Infrastructure that's been talked about since last September when the X.Org crew were drinking beers in Bavaria.
Keith Packard has taken on much of the DRI3 workload and has been working out details for sharing kernel pixel buffers, tracking window size changes with DRI3, and providing synchronization using Sync Fences. Keith is also starting to work out a DRI3 "Present" extension for working out swap buffer handling and other tasks related to presenting X pixmaps on the screen.
Keith noted in his blog post yesterday, "The first of the two new extensions is complete and running both full Gnome and KDE desktops."
For the DRI3 upbringing, Keith pas a new DRI3 protocol specification, XCB protocol and library changesl, the xshmfence library, X.Org Server changes, and Mesa changes. Depending upon how quickly the Present extension is worked out, it's possible we could see DRI3 with X.Org Server 1.15 in the fall.
Many more details on the DRI3 upbringing via Keith's blog.