I don't see resorts requiring patrons to wear a helmet for a long time. People will just take their dollars elsewhere. Even the requirement for kids in ski school to wear one can be circumvented by the parent signing a waiver. If helmet use gets above 90% of the general skier/rider using them, then you might start to see resorts making their use required. Any less than that, and it's a lot of money for a resort to lose by taking that gamble.