Wouldn't surprise me... Bumblebee is like the Wolverine of the X-Men movies - who has pretty much been the central character of the ensemble cast of all but First Class, and then milked further to have two of his own movies, yet none of the other X-Men has even had one of their own.

At least in TF4, Optimus was the main Autobot/Transformer, so Bumblebee took a back seat... and it was a little more refreshing like First Class movie (until the dragged-out, confusing plot of TF4 took over).