The park theoretically could become bigger.
The small market argument is pretty worthless, when you consider the locations of parks like CP, Dollywood, SDC, and SFNE. All parks in small market, with larger markets in a 2+ hour radius.
The best thing Darien Lake has going for it is the onsite hotel and campground which turn it into a destination for people from the Golden Horshoe, Buffalo-Niagara, Rochester, and Syracuse metros.
Is this likely, probably not. But saying Darien Lake can only stay a mediocre regional park isn't true either.