Some proposed theories I have on how the film might go:
I imagine the aspect that in the film's beginning, the group during their tour in London were getting more and more tired of Kermit as their leader, with him calling all the shots and more or less giving no creative freedom to his fellow stars and artists (at least in context of this film's story). And of course, take him for granted before Kermit is kidnapped and replaced with Constantine. As we witness in the trailer, Constantine offers them the opportunity to "do whatever you want", much to their apparent shock. They at first relish the opportunity, but of course grow to realize the hard way they need Kermit in control, not to mention begin to greatly miss their friend who's apparently transformed into some oddball with a Russian accent (I imagine Scooter's Moves Like Jagger bit is a moment where we see what awful acts the Muppets put on without Kermit, much to the others' exasperation). Meanwhile, during his time in prison, Kermit more or less grows into a less uptight, relaxed, understanding leader.
With that (great) helicopter shot, I imagine Kermit hopping onto the helicopter to try and catch Constantine in the climax, but is going to be carried away. The others fear the loss of their leader and friend, until Gonzo takes the insane initiative of grabbing onto the helicopter (exclaiming "KERMIIIIIIIT!" at the top of his lungs as he bravely leaps forward), then someone finds his or herself grabbing onto Gonzo, then things go from there, all these characters proving their strength and loyalty to each other one by one.
This is all just wild guessing, of course.