"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple Airs First iPhone 4S TV Ad Featuring Siri
Thanks @ozetadev for original video, Replaced with high quality version.
The ad shows many situations where people are talking to their iPhone 4S, asking it specific questions or describing scenarios. At the end, Apple shows Siri responding, and ends with "Say hello to the most amazing iPhone yet."