Transformers producer Lorenzo di Bonaventura recently had an interview with MTV about TF4. Here's a summary of what he had to say:
"There's a lot of new elements. I wouldn't say we've completely changed this
world, and yet it's completely different. There are new characters, new
situations. I don't think we revisit a single location. Michael really has a
great way of approaching this thing."
"The intention is this is new world, with new characters, with Mark
Wahlberg leading us. It's a different movie, but a lot of the things that
you love about the other ones are joining the ride."
di Bonaventura also said that he holds out hope for Michael Bay returning to direct Transformers 5 and 6 as well as saying that there is an open door for Shia LeBeouf to make a cameo in the fourth movie although not likely.
"I can't speak for Michael. I hope he would [direct the next two]. It would
be great, but it's certainly something in our design of this," he said. "It's
going to be an ongoing story, so the possibility, again, as long as the audience
shows up for us, there's a lot of story still to be told."
"I don't believe that would be true. You never know. Things are not set in
stone, and if something evolved and that came naturally."
On another note, Nelson, admin of Shoot for the Edit, has confirmed that Michael Bay has cast the lead female role for Transformers 4, although there has been no announcement of who that would be. Stay tuned!