I get what you are saying. But they did heavy discounts on European cruises at some point in the past as well. I distinctly remember one or two years with lots of European residents rates like Florida resident rates. I think it must have been around 2010.
Also, all the price conscious people already rebooked their reservation to the GTY rates. Which are non refundable. Those who are still with normal bookings are either clueless or don’t mind the price. So, I don’t think it will matter.
I also very much believe that
DCL will not go down in price for Europe next year. Very very few instances where cruises were cheaper in a following year than before.