What are you talking about? What does 8.3M blow past? All 3 of those parks have much greater attendance.
Well DHS and DAK if you don't go by the inflated TEA/parkhopper numbers
8.3 million for USF would have been unheard in 2011. People would have laughed hysterically at the idea of both surpassing 8 million.
2015
USF - 9.2 million (less of an increase than 2014, but still substantial)
IOA - 8.2 million (0.2% increase. Reasonable)
HS - 9.9 million (slight decrease since Frozen isn't fresh anymore)
AK - 10.2 million (slight decrease)
2016
USF - 9.5 million (very mild DA blowover)
IOA - 8.9 million (Kong should be enough to drive IOA's attendance by less than 1 million, if SDMT can do the same for MK's much larger audience. Possibly a nighttime show, too. They've been setting up for the last couple years)
HS - 9.7 million (slight decrease when LMA and Indy are both closed. What are the guests doing?)
AK - 10.6 million (slight increase due to RoL and the nighttime safaris)
2017
USF - 10.1 million (Fallon and F&F should be enough for 600,000 more visitors. Especially if Disney increases without new additions on a regular basis)
IOA - 9.5 million (Kong spillover and the first batch of MSHI upgrades)
HS - 9.5 million (slight decrease since none of the re-do should be done this year)
AK - 11.0 million (if Avatar really opens late 2017... I don't see a huge increase)
2018
USF - 11.2 million (Fallon, F&F plus Nintendo... over a million)
IOA - 10.3 million (Avengers E-ticket, possible JP enhancements)
AK - 12.1 million (Avatar boost)
HS - 9.6 million (TSPL could open this year, which will keep attendance relatively flat)
2019
USF - 12.0 million (Nintendo spillover plus MoM?)
IOA - 10.9 million (Avengers spillover, possible TL/LC revamp)
AK - 12.8 million (Avatar spillover)
HS - 9.7 million (slight increase due to TSPL)
In 5 years, both Universal parks should be past 10 million. With Nintendo plus F&F plus Fallon plus MoM on the way, USF should definitely be between 11-12 million by then. IOA will lag behind until LC and TL get refreshed. I'd even say until Seuss gets expanded/enhanced.
1.8 million is definitely close when you consider USF was almost 6 million away from AK and HS just 5 years ago. While AK will be difficult to catch up to because of Pandora and RoL, HS is definitely going to be leap-frogged by at least one Universal Orlando park in the next 5 years if TSPL is the only thing opening before 2021.