Siri needs special features to make it work properly. The 4S has two microphones. One at the mouth that is designed to get the clearest sounds spoken, another at the ear to distinquish the background noise to sort it out. That is why Siri is not considered backward compatible even though people have jail broke devices to use it. The iPad would benefit from Siri, but it would need to use a noise cancellation headset to work properly. If Apple is willing to go that route, it may happen, but it could also mean that Apple would sell it as an accessory/app with the headset. Siri on a Mac is not likely to happen. It is designed to work with a GPS system on a mobile device. No GPS on a Mac, nor any need for one. Unlike a mobile device, there is no need for a computer to have voice control since typing is not an issue. What would be more likely to be of use on a Mac, is a search engine that you could type a question and not get a bunch of unrelated garbage from sales people using buzz words.