New York tech is already pretty heavily ensconced in the mixed-use neighborhoods around Union Square— a lot of tech seems to be moving to the Financial District because big players have leased out a lot of the spaces in the area & prices have jumped. Google, Facebook, and Twitter all used to be in Midtown but moved to the Union Square neighborhood in the last couple years.

If you want to live near most tech employers, they're already all 'downtown'. Just not all the way downtown in the Financial District.