I agree on all counts. DCL is starting at a high price point (and while I'm not fond of that, the fact that I'm a gold castaway club member attests to the fact that I appreciate the value).
So I expect the key question is to what degree they are overbooking. Like you, I do expect the ships to sail full come July. It's just a question of how they will get there - and if they'll have to do some discounting to make that happen.
I also agree that DCL must be happy with the profitability on the European cruises. I'm sure they will be even if they do have to discount to fill the ship.
Here's a fun aside regarding profitability.....
I took a 4 night Carnival cruise last month. On the sea day they had an "excursion" that included a back-stage tour of the ship (including galley and the bridge, believe it or not). The head chef was "boasting" how he was about to place the weekly order for food - spending $180,000.
Based on the size of the ship and crew, that means he was feeding everyone for under $10/day. And let me tell you, DCL could learn a thing or two from Carnival regarding food - not that I have a problem with DCL food, but Carnival definitely beats DCL on variety (at the buffet, more choices in the dining rooms, longer service hours, and a much more substantial room service menu). I won't comment on quality - I'm not enough of a gourmet to compare - both are fine on that score.
I would give quality to Carnival as well the only thing DCL does better is the fast food options on deck 8 better that RCCI as well! Not RCCI regular dining!