Not really a great surprise to be honest, but when contacted by a developer about the chances of Siri coming to older iPhone and iPod touch models, Apple support responded with:

Engineering has provided the following feedback regarding this issue: Siri only works on iPhone 4S and we currently have no plans to support older devices.

Did anyone really expect Apple support to announce future product plans or feature support? In the meantime, it looks like users of older devices will have to rely on the unofficial method that may or may not be released.

Source: Michael Steeber via 9to5Mac