Do you mean a Disney-owned water park? Definitely rumors. The climate here, although wonderfully pleasant and mild most of the time, isn't warm enough to sustain year-round water parks. The ones that are located here in southern California are primarily open from Memorial Day to Labor Day and close for the other seasons. It wouldn't be profitable to use valuable real estate near Disneyland for an attraction that would only be open a few months out of the year.
Ohhh. See I don't necessarily consider those water parks since they are indoors. Nothing on the scale of Blizzard Beach or anything. That's cool though, I'm sure they will be a popular hotel choice on Harbor.