In announcing xorg-server 188.8.131.523, Keith Packard mentions, "RandR 1.4 has been entirely removed from the server. The client interface just wasn't what we wanted, and it wasn't going to be fixed in time for 1.10. Good thing the main RandR 1.4 developer was OK with pending to the next release."
The X.Org Server 1.10 release cycle is a week behind schedule right now and there are still a few more patches that need to be pulled for X.Org Server 1.10 final. This newest release candidate bumps the video driver ABI due to the removal of RandR 1.4 and pushing it back to RandR 1.3. "This prevents drivers built in the last month from running against the 1.10 server. I don't frankly know if the server is back to the full 1.9 ABI or not." The GPU vendors with proprietary Linux drivers will also need to put out new driver releases that are rebuilt for this final 1.10 ABI.
Version 1.4 of the Resize and Rotate extension provided per-CRTC pixmaps, among other changes. It also provided hope that NVIDIA might now support RandR 1.2+ due to these other changes, but now those NVIDIA customers will be waiting until at least X.Org Server 1.11.
The list of other changes in this release candidate can be found in the aforementioned release announcement link. The final release should be out in a week or two.