There'll be no end to "unlimited"
Perhaps the telcos want to return to a per-byte pricing, but the handset manufacturers won't play ball with that. So many devices and features are now based around the software being able to use web services or other web data without user intervention to keep up to date. They all expect to be able to get that data without the user's distinct permission each time, which is granted because the user knows they're not going to get stung for extra costs. If people end up on cost-per-byte contracts, then they're going to shy away from modern smartphones that have the capability of running up huge bills whilst they're asleep.