In the video interview (below) with Collider, Michael Bay spoke about returning to the IMAX format for "showcase scenes" as TF4 will be the first to use the next generation of smaller, better IMAX 3D digital cameras. He also said he would not being shooting in 48FPS (as used by The Hobbit).
The main way can tell difference if a film is true IMAX is while in the IMAX theater notice if it has the black bars along the top and bottom, much like when watch a movie on the TV. A true IMAX shot film does not have those bars, the image fills the entire screen space. So for example with Revenge, during the forest fight, the image would spread out the fill the space during the sequence and then shrink back after. Thanks to Wynton R. and Mackie U. for the links.