First of all, i read up on the next series. David has confirmed he is starring until 2010. and Chances are Donna isn't coming back (but who knows). Davros IS the creator and commander of the Daleks from the old series.
If you recall something that the Soothsayer says in the episode Fires of Pompeii, he says "doctor, shes coming back". Obviously meaning Rose. (and the rest of her crew)
and "Daughter of Landon, (Donna) theres something on your back".(what does that mean?)
Also by the way River Song looked at Donna, i think we can gather that she dies or chooses to stay behind like Martha did. but again, who knows...
Personally i think River Song knew the doctors real name because they get married in his future. Who else would you tell your real name to?
its his daughter from the episode The Doctors Daughter.
at the end she flew away and said she wanted to explore...but then again when she died in that episode she regenerated with the same body, and timelords don't age...so... who knowsss