Whenever this proposal gains momentum I think EWR and UA will be in the same fight PHL and US are in right now. Building a runway will help but you will still have airspace that is the most congested in the world and you will still have 15 aircraft in line to take off on the taxiway.
Also those proposals don't seem to offer alternatives to the lost terminal space, the lost FedEx facility, and the lost UA maintenance hangars.