I'm back. And I did not hear a single "New York" accent the entire time!
It might have been different if I'd been trading stocks on Wall Street or going to a meeting on Madison Avenue. But, crossing those streets as a tourist, all I heard was English spoken with a large variety of foreign accents. Will there be many, new, New York accents or will all the variations melt into one? The only cohesive, immigrant neighborhood I saw was Chinatown. All the other small ethnic delis and businesses seemed scattered around the island. However, three and a half days as a tourist is not enough to get to know a big city.
Perhaps within a generation we will have a new, amalgamated, Manhattan accent featuring words pronounced a bit more clearly, phrases slurred less, syllables given slightly more equal emphasis.