Last week, I wrote an article—”Siri Exclusivity Helps Sell iPhone 4S“—where I posit that Siri may have been offered exclusively for the iPhone 4S to help Apple test their infrastructure with lower user demand:

It may also be possible that Apple plans to roll out Siri to the iPhone 4 at a later date. For the initial rollout, Apple may have labelled Siri “Beta” and restricted its user base size solely to ensure their infrastructure could handle the demand. Once Apple establishes confidence in the service, they may very well open up Siri for the iPhone 4 and move it from beta to gold master.

This was just a guess, but the recent Siri outages and instability definitely support the “Beta” tag Apple applied to the new feature. We know that the iPhone 4 and iPod Touch 4th generation iOS devices can support Siri from a hardware perspective, and with the proper hacks, can also communicate with Apple’s servers. So the assumption that Siri requires the iPhone 4S hardware doesn’t hold water.

According to a rumor posted at Jailbreak Nation, Apple may be testing Siri on the iPhone 4:

Today, we have a very interesting bit of news, tipped to us by a source close to Apple. According to them, Apple is testing Siri on devices other than the iPhone 4S. The device specifically mentioned to us was the iPhone 4, but we can most likely assume that other devices are being tested as well. This means that we will potentially see a software update that allows Siri to run on older devices. Currently, it only runs on the iPhone 4S, but Apple has given employees access to a special software version that incorporates Siri’s features on to older devices. […]

At this point, we can only assume that Apple testing Siri on the iPhone 4 is a rumor, but it could be true. My only question is what will Apple use to differentiate the iPhone 4S from the iPhone 4 if Siri is made available for both devices in the future? Apple doesn’t market specs—they market experiences—and Siri is anything but a spec.