The single IP immersive lands definitely have their merits (I finally got to see WWOHP for the first time a few months ago) but they just really limit variety and options. You better REALLY like Toy Story or Star Wars to give a hoot about almost half of the future DHS. That being said, Star Wars is a perfect example of an IP that I think can support its own HUGE land, because its going to keep producing content and always feel fresh and exciting for years to come. With Harry Potter, they're still finding ways to do that too by expanding its universe. But Monsters Inc? I loved it, but how much can you really squeeze out of two movies for an entire land? A well themed ride or even small Monstropolis "street" would be okay, but I wouldn't want too much space and resources devoted to something so narrow and specfic.
Maybe I'm looking at these things MUCH too far down the road for my own good, but at some point (whether three or four more movies ever do come out or not) Avatar WILL be outdated....and they'll have an entire land that nobody cares about that seems old and outdated, and probably won't be a particularly easy redevelopment.
