I think it's way past time for a change-up.
I think Michael Bay and the Transformers franchise would both be better off without each other at this point. Don't get me wrong - Bay was an appropriate choice the first go-around. But I generally looked forward to some mindless Bay entertainment in the past with all his other films because he has one way of making a movie and that's it each go-around but applying it to different franchises and stories made it entertaining enough.
But taking on Transformers three times for Bay has exhausted the limits of anything he can bring to the table. He would be far better off approaching another franchise or genre with his signature style, keeping it fresh. Anything that has more of a story (I'd definitely take Bad Boys 3 over this) because when the films are 80% action/style and 20% story like the Transformers series has been, I really start to get bored by the Michael Bay schtick.
And the Transformers franchise could really do with a new vision and style. I am utterly bored by it at this point.