I'm somewhat surprised River will be back...I wonder if this will be the last time. If she meets Clara, and Clara is Oswin (I'm hoping she's not, and is just a relative), the Doctor will be in some sort of meta angst hell, since he first met both when they died.
If you haven't seen it yet you should check out the last DWM companion to the Sarah Jane Adventures. They go into some details about the stories that were never told, have an unpublished interview with Lis Sladen from 1993, and talk a little about story ideas that were considered when they knew she was sick but hoped she might be able to do a voiceover or a short appearance (one they had decided on was an animated special, set in DC, with Alan and Maria Jackson appearing).
Children in Need will have a Who prequel this year.
http://www.sfx.co.uk/2012/10/27/doctor-who-christmas-special-prequel-for-children-in-need/