The industry that's left is here to stay. Some stuff can't flee. And anyway, warehousing is much more important for the port, and that has been really growing.
I think this is more of a relevance play. All the uppity East coast ports like Savannah, Charleston, Miami/Everglades and Norfolk sell themselves as gateways to the Southeast/Midwest, usually with rail as the land mode partner. NYNJ has always been and always will be important because of, well, NYNJ. Ships will always come to the port to unload their NYC area cargo, and that's a massive amount of traffic, but the inland stuff is in play. Currently, ~80% of port traffic is NYC bound, but there is massive potential for growth of that 20%. If the PA can improve their inland connections, they could become the only stop ships make on the east coast, using their inherent market advantage of NYC and said connections to make stopping elsewhere on the coast a waste of time.