So for anyone who's seen the latest tv spot titled "Villain", we see a group of ships possibly terraforming earth. My theory is, that not only could the scene take place in the beginning of the film, but perhaps the Dinobots are guardians who take down that army. It would be eons untill that army returns and Optimus and the autobots awaken the Dinobots.
EDIT:
Never mind;
in that scene, at the bottom of the screen you will see something like a brick wall, meaning humans have already evolved, so it couldnt take place at the time the dinobots arrived (the scene, atleast. My theory might still stand.)

 

I don't see any wall? It looks kinda bare, probably prehistoric.

 

Never mind again, they were just rocks XD

 

Regardless of what shots are shown in the trailers, this is actually a sound theory.

If the Dinobots were assigned to earth as Gaurdians to protect against The Fallen attempting to terraform a planet with life....and they've been dormant for eons...well I think they'd be pretty pissed off if they woke up and saw what was happening.

Perhaps Lockdown captured them after The Fallen was driven off the planet, a few thousand years ago, and they've been dormant on his ship ever since.

The fact that they're covered with rust and moss and such makes me think we're missing something though. Are they really on Lockdown's ship at all? Or is there some crazy ass ancient cybertronian temple on earth that they are guarding?

Perhaps there's another ancient artifact on Earth, another one that requires the Matrix to be activated. Lockdown captures Optimus, steals the Matrix, activates the artifact....as well as the guardians? It would explain why Grimlock initially attacks Optimus...he doesn't know who's trying to steal what.