According to AICN's source, the heart of the story is pretty close to what Segel told us back in 2008. The story centers on Kermit having to reunite the old gang to save the studio, and hearkens back to the glory days of Muppet movies with the classic characters front and center. But, it's not all sunshine and roses from AICN's scooper, since they also claim that there are some flat sections to the story and some of the references are just plain outdated. The script review also goes into some pretty specific descriptions of the various cameos and is definitely spoiler heavy, so if you want to avoid ruining the fun, I suggest you tread carefully.
I grew up wanting to live in that old theater with Kermit and company, and my Animal drum set was my favorite childhood toy -- I was absolutely addicted. But I grew up, and while the later Muppet films were always good for a laugh, it just wasn't the same. Thankfully, now that the franchise is in the hands of a true believer like Segel, I'm pretty sure we have nothing to worry about - I mean, as long as Dr. Teeth and The Electric Mayhem remain intact, I'll be good.