I think the problem with single IP lands is that there aren't that many IPs that are really conducive to one, especially from a business perspective. It needs to be popular enough for the IP itself to be a draw, but it also needs to have an interesting/unique setting that makes a whole land work. Plus, there needs to be enough in the IP to support multiple attractions, shops, and restaurants.
Harry Potter works there, and Star Wars kind of works (it's a bit weaker on the setting part, especially as built, but the props help a lot). Pandora is a bit iffy on the popularity part -- obviously the movies have been incredibly successful, but it doesn't seem to have that much cultural penetration beyond the movies themselves -- but the setting works on its own even without any interest or knowledge of the IP.
Avengers Campus fails on the setting part, and I don't know that an interesting way to build that land even exists. Seems like it would always feel kind of generic.