the old neighborhoods get wiped out in the chop and change of the city. immigration continues obviously. but from what i can see, and without thinking about it very much, there's less of a tendency for people to cluster together by background. the areas that incomers settle down in seem to be a collection of people from absolutely everywhere rather than homogenous. the south bronx seems to be like that. not that i spend a load of time there. it's hard to think of an area there which has a reputation as being an enclave in the same way as polish greenpoint / puerto rican williamsburg / chinatown was. maybe this is ignorance talking, coz no-one i know every talks about the bronx. but jackson heights is the same. elmhurst is the same. i spent a bit of time in flatbush handing out food, it's babel, it's people from everywhere.
i guess corona is a counter-example. sunset park maybe. but even there it's not an enclave, there's both a big chinese thing and a big mexican thing going on. maybe this stuff just looks simpler in retrospect and is harder to figure out when its ongoing.