Apple has allegedly given the official word that Siri will not be coming to older iOS devices, at least not any time soon. I received word yesterday from someone who contacted Apple with a bug report, suggesting an optional build of iOS with Siri included, available as a paid upgrade:

Bug Title: Special Siri Build of iOS

 

iPhone 4 Users and iPod touch 4th generation users pay a fee of 19.99 to upgrade to a ‘special’ build of iOS 5.0.1 with Siri Final in it, (To avoid hackers hacking Siri onto non 4S devices illegally) **Many iPhone 4 Users and iPod touch 4th generation Users will pay for this special iOS build (5.0.1) which will enable Siri for a fee of $19.99 US dollars

To which Apple 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.

The possibility of Apple bringing Siri to other iOS devices was already slim, but this pretty much confirms that it won’t be happening. Although, Apple has been known to go back on their word before.