I don't think there will be anything new to replace 2.4ghz any time soon. FM was around from the early 80's until the mid 2000's, so protocols have a way of sticking around. I figure in another 30 years we may have a bit more reliability and lighter/better made equipment, but the 2.4ghz protocol won't get maxed out for quite a while. I would speculate the next big thing will be wi-fi or cellular based to take signal transmission completely out of the radio equipment.