Norm: I’m not familiar with Apple’s roadmap and any delays but I can say that AI takes a lot of computing power. The Siri software needs to cache data, needs to access a big dataset at wide bandwidth and needs a big processor to crunch all of the numbers. When we originally released Siri for the iPhone 3GS, we had to perform all kinds of optimizations and shortcuts to get it to work efficiently. All I can say is that it will likely run much better on a faster phone. (Source: http://9to5mac.com/2011/10/03/co-founder-of-siri-assistant-i...)
There is a big jump in performance from 3GS to even iPhone 4, let alone iPhone 5 with possible A5 processor (dual core), 1GB RAM, iOS optimization, cloud performance, and network performance--and that's not even considering if the Sprint iPhone 5 exclusive is true which would mean the device runs on a 4G network that would make this type of interaction even more interesting if interacting with the cloud in some way.