The odds are that service will be limited in addition to the coverage. The MTA will only support tapping on a per-ride basis until the feature is available across the entire subway and bus systems in late 2020, so you'll still have to pull out a MetroCard if you use routes that aren't covered. Still, it's progress -- and between this as well as rumored NFC upgrades later in the year, you might only need an iPhone to get around town in the future.