As of June 11, the original iPhone is no longer supported except in the state of California, as required by a state law. Though eventually that will expire at some point as well.
So if you live in California or can reach an Apple store there, you're in luck for now. If not, you won't be able to get a battery replacement from Apple.
Source:
http://9to5mac.com/2013/04/29/origi...reach-obsolete-status-in-apple-retail-stores/