No it didn't. I read on the main page of MacRumors in a person's review that iOS 6 brought Siri to devices that didn't have it before. I have an iPad 2 & I just hit the home screen button. It did nothing. I don't have Siri. Why did they say that this software brought Siri?
*Siri is available on iPhone 4S, iPhone 5, iPad (3rd generation), and iPod touch (5th generation) and requires Internet access. Cellular data charges may apply.
No. Prior to iOS 6, Siri was only on the iPhone 4S. With the release of iOS 6, Siri is now on the 3rd Gen iPad as well. The iPhone 5 and iPod touch (5th Gen) will ship with iOS 6 and Siri support. Siri will not be available on the iPhone 4, iPad 2 or iPod touch (4th Gen).
Just another incentive Apple want to give people to get an iPad 3. There might be some hardware reason as well
The iPhone has some noise cancellation hardware that is not present on the iPad 2. Siri (apparently) requires this. Honestly, considering they've gotten Siri to work just fine on a jailbroken iPhone 4, it's mostly just incentivizing people to upgrade. But I guess it could technically not work optimally.
I really hope Apple will bring Siri to the iPhone 4 and iPad 2 in a later update (just like how they instituted multi-touch on iPad 1).