Nuts. Well it seems the rumor of Apple working on a version of Siri for older devices was just that. A rumor. According to a reply from firstname.lastname@example.org via VentureBeat; provided by Michael Steeber ; Apple has basically put the breaks on any hints that they are working supporting Siri on older iOS devices.
I’m not fully convinced though. Knowing how secretive Apple is, there could be an effort in place for older versions that either this department does not know about, or is simply the official line. As I pointed out in my previous post, there is money to be made by capturing peoples questions for highly targeted advert services. I have a hard time thinking Apple is willing to leave that money on the table just to try to sell a few more devices.
Another reason I believe Apple could be working on this in the background is the jailbreak efforts. Many of us, myself included, will be more then happen to install this on our devices once the technological issues and legal issues with porting Siri are worked out. Keep in mind that just because you can place the files on you device does not mean you have the right to. But this legal point may not be enough to stop most people on jailbreak devices which mean Apple could have a whole sub population accessing Siri that is outside of their control or at least create a new cat and mouse game as Apple tries to block older device and jailbreakers find ways to cloak their way back in.
Time will tell of course, but I would in no way say this is the final word on the issue.