Spoilers, maybe, ish.
I saw over at The Muppet Mindset (plug, Ryan, plug) that they had been filming extra (or re-filming) some of the (SPOILER?) final scenes of the movie.
I wonder if that scene was originally written with just Piggy/Kermit, Jason/Amy, and that now they have decided to make it the "Muppets all join in at the end" moment, like in TMM. Looking forward to seeing how it pans out!!!