My other half's grandkids know the names of the wrestlers and fighters from WWE, UFC all of which is exclusively on Sky and BT. I know people aren't really saying this but it isn't as simple as put it on terrestrial and they will come - although, obviously, there is a bigger audience (only if they watch it, though).
I'd agree that the damage is done but, these days, in general, kids want things that are more instant. That's why I can see the idea of the city based 20/20. Quick sport and teams which youngsters can identify with. I am inclined to the view that if you get the marketing right the terrestrial thing is a it of a red herring