There can be no doubt that the Transformers movies are the summer blockbusters with their non-stop action, massive explosions and the latest in computer-generated effects. However, these films are not as strong as they were once before, but they can still make money. The first three films made over $300 million each, but Transformers: Age of Extinction made only $243 last summer.
The fourth film was not received well by critics and its audiences. It was by no means a reboot of the world established with the first three films, but none of the human characters from the first three films appeared, so the fourth one was distancing itself from the first three just slightly. At least Optimus Prime and Bumblebee returned, and the film ended with Optimus Prime blasting himself into space in order to find the creators of the Autobots.
This means that a fifth film is inevitably on the way. In fact, the Latin Post reports that the newest film intends to re-instate the trend of a new Transformers movie every two years. The first three films are spaced apart two years, but Age of Extinction arrived three years after its predecessor. This would mean that Transformers 5 is coming in 2016, and perhaps this franchise will take a long-term look at where the movie series is going, similar to what Marvel has been doing with its cinematic universe.
It's pretty clear that Michael Bay's directional style is the reason for the success of these films, but some fans are tired of his action-driven style, and the director has talked about moving on. In addition to Bay leaving, there are also talks that Mark Wahlberg will also be leaving the franchise. Wahlberg, who played Cade Yeager in Age of Extinction, was a definite human connection for the robots in the Age of Extinction film. Strangely enough, there are rumors swirling that Megan Fox and Shia LaBouf, stars in some of the original three movies (Fox only being in the first two), could be coming back to the franchise.
Then there is another rumor going around about casting. According to Enstars, Dwayne Johnson and Bruce Willis could be appearing in Transformers 5. These two actors appeared together in G.I. Joe: Retribution, and their involvement in the film could signal a crossover of the Transformers and G.I. Joe franchises, both owned by Hasbro. This wouldn't be the first time that the two parties have teamed up, as there was a short comic book series in the eighties distributed by Marvel that combined the two teams, and their enemies.
It is possible that this Transformers 5 might not even take place on Earth anymore, and might not have any need for human characters. As mentioned before, the fourth film ends with Optimus Prime flying into space, looking for the creators of the Transformers. It is possible that there could be a confrontation with Unicron, a gargantuan robot that could actually transform into a planet. Unicron was first seen in a Transformers animated movie back in 1987, a film which used only a handful of human characters.
I'm sure filming for another Transformers film will have to begin soon in order to meet the 2016 release date. I suppose we will probably hear within the next few months if Transformers 5 is underway with or without Bay.