Here are some facts:
The partnership with Avatar was announced when I was a sophomore in college, either Fall 2008, or Spring 2009. Development began over 2 years later in 2011, and we are just seeing this opened in 2017. For comparison, the entire Wizarding world of Harry Potter phase 1 was announced in 2007, broken ground in 2008 and opened in 2010.
Diagon Alley / Wizarding World Phase 2 was announced in 2012, and opened by 2014. These are highly immersive lands too.
Race Through New York was announced in 2015, opened in 2017.
Skull Island was announced 2014, and opened in 2016.
Star Wars was announced in 2015, and is targeting an opening in 2019.
Toy Story Land Orlando was announced 2015, and will open 2018? -- i actually don't know the estimated opening date so i hope 2018 is right haha!