You can make your ADRs any time. If they don't offer free dining they'll still offer some discount during that time that will be as good. As for when they'll announce the discounts - probably some time in the next couple of weeks, but there's no guarantee. Check the free dining rumor thread already ongoing in the news/rumor section for all current thoughts on the subject. When whatever discount is officially offered it will pop up on Intercot's home page right away.
Chris, aka Strmchsr
INTERCOT Staff: Vacation Planning, Guests with Special Needs, and Weather Guru