The Present extension is a new X extension for providing requests to put new bits from a pixmap into a window and asking for Present events to be delivered. This is part of the DRI3 initiative.
Keith Packard is to the point that the new protocol definitions are done, libxcb supports the extension, and the X.Org Server portion is working and Mesa is able to use the extension. However, there isn't yet any synchronization done to the monitor and there isn't yet any hardware driver integration.
More details on this work can be found in Keith's blog post. It's not clear yet whether this work will be finished up and merged for X.Org Server 1.15, the next server release due out around September or October.