here's a part of apost i put on TFW2005
Hello, Mr. Welker!
You have done a great job voicing Megatron in the G1 Transformers series. I know that Peter Cullen is going to voice Optimus Prime in the new live-action movie. Are you going to participate in it? [snip] I would like to contact Peter Cullen. Do you know how?
Thanks, I really enjoyed doing that voice and playing a villain for a change. I know I have been asked a lot about the movie, but at the present time I have not been offered any roles. That doesn't mean it's final, they are still doing voice casting. Peter Cullen is a hard man to track down, you might try some of the "Transformer" sites and see if you can get a message to him.