My prediction is that the Magic and Wonder will be out in the Pacific for the rest of their time in service.Given that multiple Greek Isles sailings went to VGT, I agree that I don't see double Europe.
2 years ago, when we were on the Magic and at the Gold/Platinum party, they were talking about other destinations (e.g., South America), but clearly that hasn't come to fruition.
Dream will do what the Magic used to do; split between Caribbean and Europe.
Wish, Treasure, and Destiny will do what they've been assigned for the foreseeable future.
Fantasy will kind of move around to wherever the gaps are. IIRC, they kind of did this with the Wonder for a bit.