These considerations hit the middle class harder. During downturns people leave CA, because of the costs.
There are also plenty of smart and wealthy folks who live in Colorado, Nevada, New Mexico, and Florida, in part, because the taxes are lower. As with any marginal change to a policy, you have to look at the effect on the marginal cases. You have to ask, "if taxes in CA were reduced by X%, what Y% more smart and wealthy people would choose to live there?" I guarantee Y > 0 for any X > 0.
I'm not sure why you don't think they would. It's not as though lots of people don't already commute from CT and NJ into New York. There's commuter rail, and probably less traffic than you'd get on Long Island.
CT's southwestern towns in particular used to have a reputation as the suburb for the wealthy (the so-called "Gold Coast" area), in large part because it didn't have any personal income tax at all. That's no longer the situation, but if NY decides to play the class-warfare game, the rich can take their money elsewhere quite easily.