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) Due to the negative reception and the underperformance of The Last Knight, Hasbro is looking to reboot the franchise with a different director and not letting Michael Bay direct the series again.

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

Decepticons
Megatron

Humans
Cade Yeager

Result

 * 1) The Bumbleebee movie was originally going be the last movie in the Michael Bay world, but soon it was changed to reboot the franchise.
 * 2) Hasbro now no longer wants connections with Michael Bay, so the story is entirely changed and the Transformers will be redesigned.