I know it's hard to believe for those constantly regurgitating numbers in this thread, but numbers aren't everything. Harry Potter is still arguably the most wildly popular theme park expansion of all time. Avatar in DAK, on the other hand, conjures cringeworthy reactions from most people in my experience.
Actually, numbers DO matter... People want to tout how popular Potter, Star Wars, and Twilight are, but then want to dismiss Avatar despite Avatar doing more business than any one of the Potter, Star Wars and Twilight movies (sans one Twilight movie selling more DVDs than Avatar)... Numbers don't matter if they disprove your point... But, when stating the fact, numbers do matter...
And as for popularity, let's examine:
Potter has been around for 11 or 12 years, has 7 books which turned into 8 movies, and became more and more popular with each book and movie release...
Twilight has been around for 7 maybe 8 years, has 4 books with a 5th one being a novella as part of the saga that will turn into 5 movies (maybe 6 if that make the novella a movie) and has gotten more and more popular...
Star Wars has been around for 35, has a ton of novels since the release of Star Wars in 1977, and has 6 movies, none of which are based on a book first... spawned a cartoon series and a possible live action TV show (I really hope they do this) and has become more and more popular and has stayed the course...
Avatar: 1 movie not based off a book... looks like one attempt at a novel, two books on the making of and the art of, and biological and social history of Pandora...
Two of the four above started off as books first thus gaining a fan base prior to movies coming out... The movies only increased the fan base (since I am sure there are fans of Potter and Twilight who only seen the movies and haven't read the books like a lot of people do)... And the other two only starting as a movie first... Star Wars as had 35 years to spawn 5 more movies and loads of comic books and novels... Avatar has had only 2 years in the marketplace...
The one thing I can see hurting Avatar ever gaining any traction in becoming a franchise on the same level as Potter, Twilight, and Star Wars is the length of time between Avatar and Avatar 2... The first three Star Wars movies came out 3 years apart from each other... The second trilogy (Episodes 1, 2, and 3) came out 16 years after Jedi and still three years apart from each other.. But by then, Star Wars was already extremely popular...
Each Potter movie came out 1 to 2 years after the other one... The first few Potter books came out 1 year after the previous, then final have of the series came out 2 - 3 years after the previous... With such a short period of time between each book and movie, there was no lag and momentum was able to be carried over from book to book and movie to movie (also doesn't hurt that each book only got better and better)
The same thing can be said for Twilight.. Each Twilight movie came out 1 year after the over... The 4 books were released in a 3 year period... Again, allowing for momentum to continue for the series to pick up steam and popularity...
Avatar will not have that... Avatar came out in 2009 and was not made from a series of books... Avatar 2 was scheduled to come out in 2014 and now may be 2016... Could this delay destroy any momentum Avatar built at the end of 2009 and carried into 2010?? Sure could... Could this delay erase Avatar from a lot of the population's memory?? Sure could... Any legs Avatar was getting in becoming a franchise could be swept out from under it because of the long time between movies with nothing else coming out about Avatar to keep it in the public's eye... We won't know until Avatar 2 comes out to see where it stands as a franchise...
As far as the land in DAK is concerned, no one can call it a success or failure just yet... Doing so is very premature... 1) the land hasn't even been opened yet; 2) no concept art or any kind of specifics have been released detailing what will be in Avatar; 3) no land clearing has happened yet...