Michael Bay has reponded on his website to the rumor about Mark Wahlberg having discussions with him about starring in Transformers 4:
"The Mark Wahlberg T4 rumor is just a rumor.
Mark and I are talking about another film project."
First off, everyone is assuming that he's debunking the rumor and he really isn't. Nowhere in that small statement does he say that he's not talking to Wahlberg about TF4. He just calls it a rumor. Second, remember when Bay said Megatron would not be in Revenge of the Fallen? Yea, let's just leave it at that.