Transformers 6

Transformers 7 is the sequel following The Last Knight. It was scheduled to be released on June 28, 2019.

Plot
Unicron has now awoken and the Autobots are trying to stop him.

Why It Was Cancelled

 * 1) The film was cancelled due to the negative reception and the underperformance of The Last Knight. The film did very poorly at the domestic box office (United States and Canada) and did not even meet expectations in China, the country that raised the most money for the film.

Autobots
Peter Cullen as Optimus Prime Erik Aadahl as Bumblebee John Goodman as Hound Ken Watanabe as Drift John DiMaggio as Crosshairs

Decepticons
Frank Welker as Megatron

Humans
Mark Wahlberg as Cade Yeager

Result

 * 1) The Bumbleebee movie was originally going be the last movie in the Michael Bay series, but soon it was changed to reboot the franchise.
 * 2) Hasbro now no longer wants Michael Bay to work on the upcoming films, so the story is entirely changed and the Transformers will be redesigned.
 * 3) Despite the cancellation, the film's trailer is still on YouTube.