premise: Flatbush Avenue is a major avenue in the New York City Borough of Brooklyn. It runs from the Manhattan Bridge south-southeastward to Jamaica Bay, where it joins the Marine Parkway–Gil Hodges Memorial Bridge, which connects Brooklyn to the Rockaway Peninsula in Queens. The north end was extended to the Manhattan Bridge as "Flatbush Avenue Extension."
hypothesis: The north end extension was going to be called "Flatbush Avenue Extension," Pt. 2, but wasn't.
reason: There's no indication whether it was ever going to be called anything else.