I'm not the biggest fan of Michael Bay's Transformers movies. They are mediocre at best, and that might be putting it too kind. It doesn't matter though! The movies make billions of dollars, so as long as they keep raking in the cash, Paramount Pictures is going to keep pumping out sequels. The last film that was released was Transformers: Age of Extinction, which was the start of a new trilogy that Bay may or may not follow through with as a director.
In an interview with USA Today, he reveals that he will eventually pass the torch to a new director so that he can focus on other movies that he wants to make. Here's an excerpt from the article:
Bay, 49, believes he will pass the baton for future Transformer movies to a new director while he turns his focus elsewhere.
“There’s kind of a new chapter, a new direction in movies I want to make,” says Bay, who is eyeing a passion project, a documentary on elephant poaching. “I have a lot of stories to tell. And it’s about flexing new muscles.”
I personally think this would be the best thing for the filmmaker and the franchise. I would actually like to see a fresh take on Transformers through the vision of another director. I also think it will be good for Bay to move on to different things.
He gave no indication on when he would let another director take over. It could be part 5, part 6 or maybe not until part 23.