Now, we're getting to see that in action. The developer of Air Soccer Fever (one of the best free games on WP7), Dangling Neuron (though the Marketplace has the name as Dangling Concepts), has released a video showing off real time cross-platform gaming between Windows Phone 7 and Windows 8. In the video it shows a phone (WP7) and a tablet (Windows 8) connecting and playing the game together, and it all moves pretty smoothly.
Even more impressive is that this is done without using Xbox Live, although the dev does say that Xbox Live integration is in the works, which would add gamertags, leader boards, and achievements. We're expecting more developers to take advantage of this new functionality, and it certainly could bring a boost to Windows Phone handsets.