With the science fiction elements they have already worked into the movies and space ships being a thing there isn't a single logical reason why they couldn't fill their fictional universe with more than just humans and Transformers.
In a better world they could make a movie where the action moves away from earth and features Transformers on another alien world. A world torn by civil war...
I want to start seeing live actors made up to look like aliens, like the ones in movies like Star Wars and GotG.