Also one thing to think about for the attraction coming in 2020 is the competition that they will be facing against other parks in the area. You have Hershey Park with Candymonium and their entire new themed land, which will be a huge crowd drawer for them. You also have Nick Universe at the American Dream Mall which will definitely bring in crowds due to 4 new coasters being installed there. Both of those parks are going huge for 2020, and the casual park goer would definitely be more inclined to take a trip out to one of those two parks rather than Great Adventure given the new world class attractions that are to be installed at those parks.
Great Adventure has to know what they are up against in 2020, as the local competition will be absolutely fierce in order to draw in park guests. They know they are going to lose many casual park goers to these new and exciting parks, and if they don't put up their own fight, they are going to lose a lot of crowds. I don't think that a Premier dueling coaster or a Maxx Force clone would help to attract guests away from the other parks. Hell, even the Intamin sit down/invert concept might not do enough. This is why I think Great Adventure has been saving up for this year, knowing that it is now or never to install a world class attraction.