According to recent news, "An Apple spokesperson has told T3 that the MacBook Air's multitouch track pad is software, not hardware, based.", and despite the fact this wasn't quite a secret for many, it's nice to know it from official sources inside Apple. These being said, the next step should be obvious...
While there's no official confirmation yet, prepare for a software update that will allow you to experience the multi-touch features of the MacBook Air in all their glory on your older MacBook or MacBook Pro computer!
How old? Well, if your MacBook already features two-finger scroll, horizontal scrolling, zooming, and secondary (right) clicking via its Trackpad, it should be enough. Don't worry, you'll find out about this as soon as it happens, and I hope to be able to give you some hints about when is this going to happen, in the meantime, so don't forget to come back here from time to time, or subscribe to our FeedBurner feed!