Rumors of a cheaper, 4-inch "iPhone 6c" model of the next generation of iPhones began late last year, backed by a few sources out of the Asian supply chain who manufacture the smartphones. More recently, however, reliable KGI Securities analyst Ming-Chi Kuo claimed these rumors as false, noting that Apple will stick with 4.7- and 5.5-inch models this year.
While the iPhone on Apple's website in question today could in fact be the accidental unveiling of a new iPhone 6c, it's highly unlikely the company made such a slip-up in revealing an entirely new iPhone. It's more likely a curiously egregious Photoshopping error having to do with one of Apple's website designers, and will no doubt be taken down in due time.
Update 10:05 AM Pacific: Apple has removed Touch ID from the iPhone 5c render as expected.