You pay your money and make your choices.
Siri will only work properly on older devices and that is if Apple allow it.
A workaround will be to set up your own proxy server, get a device ID from a 4S (every 24 hours), change it on the proxy server (every 24 hours), and all this just for Siri?
Its not impossible for Apple to check that the request has come from proxy server either, so then thats that 4S never to communicate with Siri ever again.
Enjoy the wait.
I will enjoy the wait, it's no skin off my nose.
I find the willy waving on this forum hilarious from those with the latest iPhone model, it happens every year. I've owned the iPhone 4 since day two (wasn't queuing on day one) and as I said, it's not enough of an upgrade for someone who buys their phone outright.
The next model will be the true next generation iPhone, not a stop gap like the 4S. It's not a case of not having the money to spend, it's a matter of making the right choice. I'll enjoy the wait, as you say, and I'll also enjoy the larger screen, redesigned chassis, improved design, and faster performance ... only I won't log on here to belittle those with (now) inferior iPhone 4S's and willy wave over a materialistic device just because I have more features than someone else.
If Siri comes to the iPhone 4, be it officially or otherwise, so be it. I'll use it. If not, I'll use it when the next generation model comes out. There's more to life than having the latest iPhone to boast about.