If EU wasn’t opening with a Monsters land I would be more skeptical, but I think it is very possible that Disney builds a Villainsland either at MK or DHS in the coming years
I've never understood the persistence of the villains land concept. If memory serves, it actually was a real idea tossed around by Imagineering. But I think the concept in its entirety is somewhat questionable.
First, you have the problem of environment. Disney Parks spaces are supposed to be beautiful. When Disney Parks spaces are not beautiful, it often provokes a visceral reaction on the part of guests. Take the response to Walt Disney Studios Park and Disney's California Adventure when they originally opened. Both had spaces that were ugly, and thus those parks were maligned. Disney's Animal Kingdom dabbles the most with rugged environments, but no one questions the beauty of the environments there. Dinorama, despite being rather thematically clever, is hated because it's ugly.
What would a villains land look and feel like? The land would need show the "villainishness" in the environment. Is villainy good or bad? Well, bad obviously. So, the environment would need to demonstrate the decay associated with exploitation, theft, and hatred. If it didn't do that, the moral of the story would be villainy is a good thing. So, you can expect broken down and degraded buildings. Signs of evil and oppression. And because this is a villain's land, we can assume that any resistance is futile. So, there would not even be the semblance of hope that the villains can be defeated. Even as villainy is ugly, so too will the environment be ugly. I don't see how you get around this point.
My second critique is related to the thematic concerns. Villainy itself is not an adequate unifying theme or message. What would a villains land be communicating to guests? "If you put your mind to it, you too can be sadistic enemy of goodness." Disney villains were traditionally designed to be textbook definitions of evil. Evil should not be celebrated in a Disney Park. Is it we (the guest) are journeying into villains land in order to defeat the villains? That's better, but it's not a unique concept to a villains land. Even Buzz Lightyear Space Ranger Spin deals with defeating an enemy or "villain." Why is an entire land dedicated to villains better than placing attractions about confronting evil throughout the resort? Especially when those attractions could be tailored fit the environment.
Adding a major (Galaxy's Edge or Pandora) size land to each of the four parks simultaneously would probably cost less than adding a fifth gate, would be logistically simpler than adding a fifth gate, and would likely have a similar marketing draw of adding a fifth gate (especially if they are advertising all four additions as one big resort wide addition)... nonetheless, I don't even see Disney doing that...
Exactly. Building new theme parks includes significant spending on infrastructure. Things like parking, connective areas between attractions, security areas, ticket booths, etc. all add to the expense. Disney has an advantage because it already has all this infrastructure in place four times over.