Everyone's saying Siri won't come to older iPhones, but this report may be premature. It's based on an email Michael Steeber received from Apple support about a bug in Siri. The customer service rep was told by Apple's engineering team that "Siri only works on iPhone 4S and we currently have no plans to support older devices."
Most people are focusing on the "have no plans" part of the response and overlooking the key word "currently". Yes, right now, Apple doesn't have plans to expand Siri, but these plans could change next month. It's not like Apple hasn't said one thing and done another before - remember the iPod,