I don't think it will be some kind of advanced video-game like virtual reality, because video-games are pretty much our generation's thing. When virtual reality comes along, we won't be banning it, we'll be the ones playing it (likely with our children looking down on us and our old-fashioned, game-playing ways).
I think it will have to be something completely different to anything we've experienced in our youths, like how different video-games were to anything that came before them, and how different movies were to anything that came before them. Unfortunately, this makes it kind of hard to guess at. I'll go with... Walrus Skating.