The entire deposit is non refundable. You can change sailing dates or change ships for a $50 per person fee and the deposit is applied to your new dates but no refund.
My choice would be to book with Carnival and watch the price myself. Agents are booking many people so they don't always have you as a priority. The price drop will not happen unless you submit the online form.
54 Carnival: Mardi Gras, Ecstasy X2, Fascination X6, Celebration, Elation X5, Glory X5, Fantasy X4, Valor, Holiday X3, Imagination, Liberty, Spirit X2, Freedom, Destiny X2, Splendor X2, Dream X2, Conquest, Legend X3, Victory, Sensation, Paradise, Inspiration, Magic X2, Triumph, Miracle, Breeze, Sunshine X2
6 Norwegian: Sky, Jewel, Dawn, Epic, Pearl, Breakaway
7 Windjammer: S/V Legacy X3, S/V Polynesia, S/V Caledonia, S/V Diamant, S/V Sagitta