I applied my discount package to my April 2015 trip on January 1. I've heard some people say they had issues booking their trip and then having the discount applied, but mine took less than 5 minutes on the phone and took almost $1000 off my bill!
We are also looking for April, the week of April 2-10, but we are only planning to DW for 3-4 days of that, most likely at the end of the week based on the crowd calendars I've seen. Hoping for some discounts since I think most people are on Spring Break the week prior.
Discounts came out in January this year for April/May trips. If you want a specific resort, book it and hope it has a discount, but be prepared for it not to have one.