The most recent info I can find on this is that Siri is only available on iPhone 4 through jailbreak, but once done, you can't get to the Apple server. So no to Siri on iPhone 4. But all posts are a year or more old. Any positive updates here?
As of Jan 2013, is Siri available on the iPhone 4?
No unfortunately not. The apple website still states siri on 4s and 5.
No, it's only available on 4s and 5