Seems to me, all the parks should be open until midnight or later... Disneyland, most of the year, is open until midnight, why not WDW parks?
It is especially difficult when WDW is 3 hours ahead of Disneyland, meaning, that, even 12pm is only 9pm for us Californians 
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WDW hours apply to EST only.
No other time zone is relevant.
There are guests from all over the world that have to adjust.
Honestly I wouldn't be surprised to see hours shrink back to Epcot standards. Look at Universal and all the other parks. The other parks also make some good money on renting out sections of parks after closing.
Wouldn't be surprised to see more pay to play like we've seen with After Dark, Early Morning Magic, more parties .... think they can ALL be successful once all the new lands open.
Labor costs, not only the park CMs you see but consider how much will be saved by reducing manpower hours behind the scene, security, all the bus drivers and transportation ..... transportation savings alone would be huge. Nothing can be cleaned, painted, greased and oiled, repaired etc until all the guests are done.
CM morale, if you know the ones who work evenings it is no fun not only the hours but by then the grouchy guests. Remember even after the park is closed they have to clean up and close out so they are still working when guests are sound asleep. Throw EMH in there .......
Disney already pays less than other parks etc, anything they can do to create a better working environment for retention. There is a reason they expanded the DCP program a couple years ago, they needed the manpower.
Overhead to fully operate the park. Only way to reduce those costs is hours.
MSEP is gone, SW Night time is not wowing, Illuminations once a night and who knows what ROL will pan out to be. Perfect time to ease into new routine. I could see MK doing one parade followed by fireworks and park is closed just like Epcot. Given current situations I think early hours could work out ... if you are still wide awake they would be happy if you go to Disney Springs and spend money ... good reason for the new buses to go from parks to DS later afternoons on.
And lets not forget that attendance is way down and therefore income ... no need for long hours because with lower crowds guests can get more done.
DISCLAIMER: All opinion and observation based comments.
Myth? Then how much do they pay all those college program kids?
A little more than minimum wage and varies by assignment BUT there are also perks that would be considered wage in a different way. Their rent is deducted from their check but after comparing housing vs DD getting an apartment with roommates it was a way better financial deal to live in housing. They also provided transportation for all those without cars. They also get free entry to parks, free tickets, huge discounts for their family at hotels, holiday discounts that are awesome to shop and eat. DCP can live, pay their bills and still have money to enjoy their time there. DD had a blast and it was no financial strain.