Even if Black & White's future is bleak, I do not remember ever reading that the IP for B&W has been sold to, or remained with EA Games.
My bet would be that BW3 is possible, yet implausible. (How I hope that I am wrong!)
If you are waiting for an official message from Lionhead, be prepared for something like: "We currently have nothing planned for the Black & White series as all our time and effort are currently going into the development of Fable 3 and Milo."
Then they will go on about how wonderful their latest games are going to be, and finally end the statement in regards to B&W with something in the line of: "Never say never."