Looks like we have our answer in regards to which side the new Transformers 4 vehicles are on.
In the following Transformers 4 set video we see Optimus Prime along with the new Bumblebee rolling out with the Freighliner and other sports cars.
Many online speculated that the black Freightliner was Motormaster with the sports cars the Stunticons, but the following video seems to say that the vehicles are Autobots as we see Bumblebee leading the pack.
It's possible that the Freighliner could actually be Ultra Magnus.
Transformers 4 has a Summer 2014 release directed by Michael Bay and starring Mark Wahlberg, Jack Reynor, Nicola Peltz, Sophia Myles, Li Bingbing, T.J. Miller and Kelsey Grammar.