Or until the next glacial period, when all of New York will be scraped clean down to the bedrock.
Perhaps. Last time, NYC was about the southern limit - Lawn Guyland represents the terminal moraine (actually, a couple of them IIRC).
Well, it was close enough last time for the glacier to scour rocks in Central Park, so I think it is quite likely it would happen again.
Well, with Global Warming the city will probably be flooded out first (and perhaps buried in sediment) before a new ice age buried it under ice. So…maybe the glaciers would eventually uncover what the seas covered up for those theoretical alien visitors…
-XT