Or, short version: take Guardians of the Galaxy trailer; replace Guardians with Autobots. Done.
Someday we will get a Transformers movie that focuses on the actual stories of the Transformers with little to no humans...someday. On the bright side my cousins wouldn't love Transformers if it wasn't for these movies so its awesome to share that love with them! Even if I'm not a fan of them.
Take a good long look at just how many films a year, how many films in cinema history rather that have been made in live action and haven't starred humans, "red carpet humans" in the majority of the lead roles. Unless you expect optimus to show up on kimmel, they will need a bankable/pretty star and not just as the 'voice of a car'.
I'm sure someday fans will get that kinda TF film, oh wait, they already have, a few of them actually they just happen to all be non live action 150plus mill productions. Unfortunately human lead films are the circumstances these films will currently have to fall under. The same way all other big live action films do.
Note, pacific rim was sold on humans as well, godzilla, avengers, that's the way it works in non pixar movies.
90% of hollywood films tend to fall into romances in some form, yea don't see that happening in the tf mythology all that much without humans. Bay isn't going to reinvent the wheel of how hollywood works with a property that makes paramount all their money. Till then fans will rage and the GA will flock and Transformers films will exist. Kids seem happy.
Guardians of the Galaxy, from what I can see is not only lead by a pretty red carpet/jimmy kimmel male actor(same as here), but it has a bunch of other actors in make up. That being said, there is a tree and raccoon... The tree is a walking drinking game. The raccoon looks a little one note to me(angry) but then again both Bee and Optimus.....
This especially applies when it comes to the highest grossing live action films. From Avatar to Pirates to Startrek...it's why James spader won't just be doing voice work in his up coming role as the main villain. Hollywood.