Apple won't even claim this. They just waffle and avoid the question. I don't know why it is so hard to believe that Apple would do this to give more incentive to buy the 4S. It is the flipside of the famous Google criticism "if you aren't paying, you are the product". With Apple, you get the product, but you are going damn well pay for it. Whereas on my Android my crap prepaid 600 MHz phone runs Voice Actions just fine.
Waffle? Apple never waffles. Apple just says nothing at all.
I have no problem with Apple purposefully limiting Siri to the new iPhone and I don't really understand people who think that because the hardware supports it they should get it.