In case this isn't a joke...
The 'Excavator' coaster has been rumored for DAK for years and years.
The Monster Inc. Door Coaster rumor is... ridiculous. A "door coaster" is a hanging coaster (like Peter Pan's Flight, but... a coaster). But RnRC is a tracked coaster. It's *impossible* to just retheme RnRC to a 'doors coaster.' But, this was a long time Jim Hill rumor who held onto it for years after our trustworthy insiders told us a Monsters Inc land was on indefinite hold.
The coaster at Pandora was the original E-Ticket that went around the floating mountains. It's too late to add that now.
So... if this is a genuine insider scoop... your source, I'm sorry to say, is 100% unreliable.
Guest-facing CMs generally only know what they read here and the crazy rumors on the Internet. Upper management most certainly does not keep them in the loop as to future plans except maybe for the very area they are assigned (e.g., a CM working in a theater may get notice the theater is closing as part of their reassignment). And blueprints for rides in different parks for several years to come aren't left in the front-facing CMs break rooms.
Oh, one more thing: Disney is beating back guests overcrowding MK. Huge hikes in costs have not deterred the crowds. WDW had to instate a reservation system to lock people out on peak days. So... WDW isn't worried about Epic Universe. Just like WDW had nothing to fear from Universal Studios or from Islands of Adventure.