I believe Justice League is by contract, as they have only two parks left to fufill the contract (which those two have been rumored to be Magic Mountain and Great Adventure).
While I can be wrong, it may not be a shock that they wish to extend the contract for additional parks in the coming years, although I highly doubt that.
In the article, it's also said that it's not a worlds first, but it's something that is seen from other various amusement parks; which could be something to clue in. Looking at the size of it, it can very well be a coaster. And that actually makes sense; as it is the parks big 50 next year, combined with the fact that it's been about 5 years in essence since they have gotten a major coaster.
What type of coaster, should be looked at what may of opened this past year..