Hi Erin,
Welcome to the Disney Parks Moms Panel. I'm glad you popped in with your question!
The free dining promotion is quite popular around here but no news has been released for 2015. If this special offer does become available, your reservation can be modified but it will not be canceled. Just call 407-WDISNEY (407-934-7639) and a reservation specialist can change your existing reservation to the special offer if it is available. Your dining reservations should not be affected whatsoever, so there's nothing to worry about there!
I would recommend that you keep an eye on the
Disney Parks Blog for any announcements about the free dining special. Since only a limited number of rooms are available, you'll need to make that call as soon as you can.
I hope that you'll be able to get the free dining plan for your upcoming vacation. As a tip, it's always a good idea to compare prices if there's a room discount (like 25% off) to the free dining plan and go whichever one is the better deal. Wishing you lots of magical memories.
Happy planning!
~Carrie