I hope someone's able to activate Siri on the iPhone 4. Its a cool feature for sure. But even then, I'm not sure how much use I'll have for it. I have Dragon Go installed already for "texting on the go," but I rarely ever use it (I've also tried Vlingo, but I feel Dragon Go is more accurate. BTW, I believe they are both free on the app store right now if anyone's interested). I've never used the built-in voice-control either.
It'll be a nice add-on to have Siri, but if its impossible to get, I won't sweat it.