Well if you take a look at the past attendance numbers, even before LMA (I believe in 2005?), they aren't that much different than what they are today. They were around 8-9 Million.
I think the only way Disney is going to kick it into gear is if a Uni park passes DHS. Which at the current rate, might be about 4-5 years, which based on the timeline of rumors around here, seems to be the time when Pixar/Star Wars will be almost finished or complete.
The real question is, will a Uni park pass DHS before that point while these things are under construction? That will be interesting to see.
If 2021/2022 is the time the good stuff opens (Star Wars Land and a Pixar D/E), I definitely think at least ONE Universal Orlando park will pass DHS in attendance according to TEA numbers. Most on OU and other insiders are saying Universal Orlando's parks have already passed DHS and DAK. DHS really gets 7.5-8 million/yr, so by official TEA numbers, both UO parks are around DHS already.
By 2019, one of the two should pass DHS. Because by 2019, Indy should be gone. LMA will be gone. GMR could potentially close down for either a major upgrade or a replacement. B&TB could go down either as a cost-cutting measure or for a Moana/Tangled replacement. Same for Mermaid. Muppets might close down for an upgrade at some point - or replacement.
For 2018/2019, DHS' lineup could very well be:
- Star Tours
- Jedi Training Academy
- Frozen Sing-a-Long
- HITSK play area
- TSMM
- One Man's Dream
- Disney Junior Live on Stage
- Tangled and Moana replacements (likely cheap) for Mermaid/B&TB
- RnRC
- ToT
With only 7 attractions appealing to someone over the age of 8, I don't see how DHS won't noticeably decline in attendance. And with the lineup Universal Orlando has going, plus more hotels and an immersive water-park, I don't see how they won't continue to go up.
2015
USF - 9.1 million
IOA - 8.4 million
DHS - 9.9 million
2016
USF - 9.5 million
IOA - 9.0 million
DHS - 9.8 million
2017
USF - 10.3 million
IOA - 9.7 million
DHS - 9.7 million
2018
USF - 11.4 million (Nintendo grand opening, F&F and Fallon spillover)
IOA - 10.5 million (Avengers E-ticket?)
DHS - 9.5 million
2019
USF - 12.2 million (MoM plus Nintendo spillover)
IOA - 11.2 million (Avengers spillover plus something new for IOA)
DHS - 9.4 million (TSPL should open this year, so a mild decline)
2020
USF - 12.7 million (MoM spillover, something in the MIB/Springfield plot?)
IOA - 12.0 million (something major for IOA?)
DHS - 9.2 million (calm before the storm)
2021
USF - 13.2 million (spillover)
IOA - 12.5 million (spillover)
DHS - 10.6 million (Star Wars Land)
By 2021, it'll be too late. USF and IOA should both be either equal with or ahead of DHS. AK and Epcot aren't really achievable currently. MK is never happening.