I don't think it's a new attraction or festival - they wouldn't need call center reps for those things.
Whatever it is, it's going to be within the next 12 months, at Epcot, and be instantly popular with a large number of people.
Imma go out on a limb here - and let me say that I have absolutely no idea what the announcement is - and say it's Barack Obama as a Candlelight Processional narrator.
Reiterating: I have no idea what the announcement is. I just think Disney is considering having something on the other side of the aisle, as it were, for when HOP reopens. And that'll be around this time. Again, total guesses, no information at all.
ETA: It just took me 31 minutes to make ADRs on MDE for the all the open CP dates. That's why they're going to need call center staff.