It looks as if the big villain reveal is coming on Tuesday as a Transformers: The Last Knight viral teaser has been released featuring morse code that when decoded reveals:
"I'm coming for you May 31st."
The Transformers social networks also included "Something wicked this way comes" on the post, which more than likely means the villain of the movie.
It's long been speculated that Unicron will be the featured villain in Transformers 5.
Transformers: The Last Knight has a June 23, 2017 release directed by Michael Bay starring Mark Wahlberg, Stephen Merchant, Isabela Moner, Jean Dujardin, Jerrod Carmichael, with Peter Cullen returning as the voice of Optimus Prime.