The folks at Unity Technologies have released a new machine learning toolkit in open beta that's designed to let Unity devs (making games or anything else) incorporate AI agents capable of teaching themselves new tricks.
It's called the Unity Machine Learning Agents SDK, and it's probably worth a look if you're at all curious about where Unity is at with machine learning or how you might be able to use it in your game.
Note also that some AI-focused devs have celebrated machine learning's value not just in designing better game AI, but in designing better games.
"Someday, designers will have vastly more powerful tools at their disposal, including some tools to help evolve and grow and tune and optimize the [game] design itself, not just the content," seasoned AI/game dev Paul Tozour told Gamasutra in 2015. "And that will have to involve a lot of machine learning."
For now, this beta version of the Unity Machine Learning Agents SDK is available as open-source software (under the Apache 2.0 license) via Unity's GitHub page, For more details about how the new toolkit works and some examples of how you might apply it to your work, check out the Unity blog.