There will ALWAYS be a ship doing those 3/4 night cruises from Port Canaveral. That is
DCL's bread and butter ship and likely their most profitable over all. (Treasure prices are really high- but with half as many cruises I am guessing Wish does better overall for the bottom line.)
Totally disagree that Wish will be the one that struggles the most- I think that will be the Dream sailing from FLL. Why chose the Dream when the Destiny is right there as well sailing to mainly the same ports and for similar pricing? I think they have set the Dream up the worst in this batch.
If the Wish really does go to Europe for Summer 2027 (which I think based on this schedule seems extremely likely) then there will 100% be another ship moved into that spot. Whether than be Wish #4 if its ready or Dream or Fantasy- it will be one of them.