Our friends at jailbreaknation.com shared an interesting story they got tipped to by a source close to Apple. According to the source, Apple is testing Siri on devices other than the iPhone 4S. Currently, Siri only runs on the iPhone 4S. While hackers are currently trying to get Siri working on other iOS devices, it seems like Apple is testing Siri on the iPhone 4 as well.
It would be surprising if Apple decides to release Siri for other iOS devices any time soon, because Siri is the main reason a lot of people are buying an iPhone 4S.