The new Monsters show is simply part of the new land...
disneyparksblog.com
That’s right, humans will be able to enter the world of Monsters, Inc. when it is added to the south side of Disney’s Hollywood Studios. Building off the exciting announcements from last summer’s D23: The Ultimate Disney Fan Event, the new land will include the coaster we’ve all dreamed of – a suspended ride recreating the door vault scene – plus dining and shopping and a whole new theater show.
If one want to be doubtful there will be a show... fine. Be doubtful. But it's not some phase 2 vapor imagineering. 
Monsters and Muppet Updates for Hollywood Studios
Enter the world of Monsters, Inc. when it is added to the south side of Hollywood Studios, while The Muppets move to Sunset Boulevard.
