I have taken the plunge and drastically limited ds1's online time. He was increasingly suckered into an online world and all his old hobbies seemed to dwindle. He still does football and rugby but that's about it!
After an initial period of denial (only an hour so not too bad all things considered) he is struggling to find what he wants to replace gaming with in his affections. I think it's a case if the world being such a big place that he doesn't know where to start. I have promised him a list of things that he can use to pique his interest with, and then maybe an afternoon at the library to see what he comes up with himself.
What does your ds do with free time? It doesnt need to be sporty or even outside the home- it's just that I could come up with a list of so many things I want to do/find out more about/ research/ learn how to do for myself and I am sad that I've taken my eye off the ball and let online stuff cancel out all his lust for life.