According to his statement, he met and talked with a Product Manager for the film and was told that the Constructicon combiner will be similar to that of Energon Optimus Prime's combined form.

As stated by s250:
In the Gestalt version, most construction vehicles [are] just transformable drones as a part of Devastator, [with] no robot mode. These vehicles will get Deluxe versions [that] can transform to robots, but I think Deluxe version [won't] combine.
Very hard to say how accurate this information may be, but s250 has provided very reliable information regarding future releases in the past.
We'll keep you posted as more news develops.