Indeed.Machine learning is a job that required much computing resources that most players's machine can not handle. And there is no game can use machine learning to improve AI now. But it is interesting may be possible in the next 10 years.
Though my main thoughts were for the developers/testers to train the AI and then make it available in the main game. However even this method has its own challenges as training AI using machine learning is not straightforward right now. And this still does not circumvent issue of computing resources necessary, only very wealthy gaming companies who are willing to make large investments to develop their AI could even consider it right now.
The use of Machine learning in video games is very much in its infancy, but the potential is staggeringly high, it will just take time, likely decades as you duly noted for researchers to come up with new more improved methods and streamline everything as much as possible.
I really look forward to what the future holds, we are in such exciting times.