It will never happen and even if it did, it would be un-policeable (if that's a word). There are lots of casual cyclists, like myself, who only go out occasionally and who would just risk not having insurance for the few times they went out. You would have to have different levels of insurance for adults and children and I foresee premiums being prohibitive for children, in time. This would potentially affect the fitness of our children when the Gov't are trying to encourage them to get away from sitting in front of screens.
Aren't we taxed and insured to the hilt? Lets just keep this one piece of freedom.