Here's the problem. Let's say they get only 80 requests for twins on a specific voyage. Now you've got 20 cabins (40 people) who want queens just as good as their neighboring cabins, and you've stuck them with the old-style splittable beds, with "the ridge". What's worse, you now have
onboard complaints instead of on-the-phone complaints from the people who thought they could reserve twins on the Dream.
DCL does not like onboard complaints, because those are spread at dinner, in the bars, etc. Yes, there will be some onboard complaints from people who thought they could get twins, but if DCL is smart they will email those demographics beforehand. Plus a complaint of "I thought I could get twins like on the Magic" isn't going to be as loud (or repeated) as much as "How come my neighbors have a better mattress than I do?"
And now you've created more cabin categories for DCL, creating more confusion from a cruising public that's already confused by 6A, 6C, 11A, etc. Plus if the prices are too high, it will drive customers to the Wonder/Magic, or to queen beds on the Dream. So no, they wouldn't make a killing.