I wanted to backtrack on my statement earlier in this thread saying it doesn't really matter. TDO had a miserable quarter and Easter fell in it. It might be hard to believe, but this Summer was the first one since 2015 where WDW hasn't had a new ride open in time for or in the early/mid part of Summer. Sure SW:GE will technically open in Summer, but it's late summer and the damage was already done and evident in the recent quarterly report.
Starting with 2014, here's what Disney's PR team has had to work with each of the past six Summers (defining "summer as in opened before end of quarterly earnings period):
2014 -
Ride: Seven Dwarfs Mine Train
Other: Frozen Summer Fun/24 Hour Disney Day
2015 -
Ride: None
Other: Frozen Summer Fun
2016 -
Rides: Frozen Ever After, Soarin' Around the World
Other: Disney Springs finished construction
2017 -
Land: Pandora - The World of Avatar, featuring two new rides
Other: Happily Ever After, Rivers of Light, Mission: Space Update, Miss Adventure Falls
2018 -
Land: Toy Story Land, featuring two new rides
Other: UP! A Great Bird Adventure
2019 -
Ride: None
Other: Lightning McQueen's Racing Academy
2015 was just about rock bottom for WDW when you put into context where Universal was at having just celebrated Diagon's opening the year prior and Comcast really starting to see the full potential as hotels were being built at a rapid pace and this was also the year when work on the ground began for Volcano Bay. Not so coincidentally, Disney also had a poor Summer in 2015 and this has since prompted a high amount of money being poured across ALL parks, even their water parks. Now of course Universal didn't open a ride in 2015 either, but if I remember correctly, they still had a solid enough summer.
So considering two of Disney's recent weak summers were when they didn't open a ride or have anything much at all (that's actually open) to push, I actually do feel like Spring/Summer is still when rides should aim to open in Orlando. Here's the thing: Theme parks are getting EXTREMELY expensive and Orlando isn't the most fun place to be in the Summer months. You have to give people a reason to be there. There's also only one major holiday travel week all summer and i'll include Memorial Day weekend as a major travel time (I know not part of Summer technically, but it's part of "theme park summer"). So the park are good during that time, but the rest of the summer, you gotta give people a reason to spend there money in a miserable climate when there are so many other travel alternatives in this world.