Sometimes they get it right, and other times (no Star Wars movie this past December = Aquaman billion dollar domination) they misfire.
It’s possible one or more of those films will move again, and it’s also possible more films will join them on the Memorial Day 2020 calendar.
There’s still a year to go before any of that happens, and studios always carefully watch the competition, read the tracking tea leaves, and do whatever they think is best for their films.