The history of AI goes in cycles. Someone has a good idea which solves some problems, followed by "strong AI Real Soon Now" enthusiasm, followed by that idea hitting its ceiling. AI has been through search, backtracking, the General Problem Solver, hill-climbing, and expert systems. Each was overhyped at the time, and each hit its ceiling.
The big difference this time is that the ceiling with machine learning is high enough for large-scale profitable applications. That wasn't the case with the previous rounds. AI used to be a dinky field - about 30-50 people each at Stanford, CMU, and MIT, plus a few tiny groups elsewhere. Now it's a huge field with big companies and big profits. That makes it self-sustaining.
Hinton has a point in that we're missing something. Back-propagation is an extremely inefficient method, especially since the slower you do it, the better it seems to work. More generally, most of machine learning is "turn the problem into an optimization problem and bang on it really hard with lots of compute power". This works for a useful class of problems. But it has limits.
How long until the next big idea? The last "AI winter", after expert systems, was 15 years.