Have just read about this, not sure if this is a rumour or if anyone else knows about this:

Joan Collins is tipped to play a baddie in the next series of Dr Who.
The 74-year-old actress is apparently being lined up to star as The Rani, an evil Time Lady who'll battle the Time Lord (David Tennant).
The character was last seen in 1987, with Kate O'Mara in the role.

Oh...goodie!
I'll be looking forward to that!

Thanks for the heads up