Not really, the cure is designed to cure the Trog disease, which only exists around The Pitt. It can cure other mutations as well, but the people of the east coast wastelands don't seem to get things like third toes or w/e that often.
All the cure would do is mean Ashur wouldn't need to keep enslaving people, which would put a hurt on the slaver economy, but otherwise wouldn't change that much. We would hear that The Pitt has gotten a lot better, but its not going to have a massive change on the wasteland.
I also don't recall him building railways, only using pre-war ones when he found them.
Well, i've said it so many times by now, and don't want to type the whole thing out again, but, Bethesda, IMO, clearly established the places they wanted to be considered the "big" regions of the east coast, and those were D.C., The Pitt, Ronto, The Commonwealth, and The Broken Banks. If they really wanted to do a NYC Fallout game, they would have suggested as such in Fo3, when they were building the lore of the east coast.
Does that mean we will never get a NYC Fallout game? No, it just means I don't see them doing it based on the foreshadowing/lore building in Fallout 3.
-Fallout 3 was set in D.C., and with The Pitt, and Point Lookout covered Maryland, Virgina, Pennsylvania, and gave us lore about New Jeresy, covering what amounts to the cetral third of the east coast.
-Fallout 4 is set in Massachusetts, will likely give us a DLC to New York State, and give us background lore on nearby states like Maine, Vermont, and New Hampsire, covering the upper third of the east coast
-Fallout 5 will likely be set in Charelston South Carolina, give us lore about North Carolina, and we will maybe get a DLC to Atlanta, covering the lower thrid of the east coast.
It just makes sense based on what Bethesda is seemingly doing IMO.