Three hour delays at JFK go under the heading of "sh*t happens." And lots of times the GAs do not know any more than you do nor will they know what is happening until it happens.
NYers either get used to it or fly with another company (which will have its own issues just as bad as this). Just plan your life so as that sort of thing will not cause any real problems and try to avoid the rush hours at JFK (4-9PM).
Says the man who has a 730 out of there tomorrow evening.