Filming is currently underway in New York, and the Doctor Who production team have put out a casting call for Alex Kingston's photo double which will also be required to drive for the actress. Kingston herself is rumored to be appearing on the set imminently.
The episode is the fifth of the series and sees the departure of River's parents, Amy and Rory. It is written by Steven Moffat and features the Weeping Angels.
Moffat recently said that the departure of the Ponds doesn't necessarily mean the end for River Song.
(Source: Doctor Who TV)