The only park they are going to effectively get people out of is DHS, which at the moment needs all the people it can get.
Epcot is known as a night park for touring World Showcase and MK is MK so things won't be changing much there. Like I said about Pandora, I don't see this doing much but taking people away from DHS.
If they open a new show to the public and publicize it they can redirect guests. If they just offer it with barely a whisper, then no. But if they put on a big blog post about it then the people will come.