next to nothing has been said about the incorporation of this new framework, so ....

is it only for builders of Android apps interested in following Google's Material Design standards,
or something else in addition?

Simple, clean and easy....

I predict it will become very popular.

It's a framework with well thought out visual effects en cool transitions. It is not for android apps but can be used to create visually appealing sites.

I agree with Twinstream's prediction

well, it seems kinda like it's definitely for Android apps, but that's also like saying a wheel is definitely for a car, but maybe a lot more
still not everyone sees its appeal as universal, and it does seem to have its problems
https://www.justinmind.com/blog/flat-design-vs-material-design-whats-your-flavor/

https://www.markupbox.com/blog/top-5-popular-css-frameworks-of-2017/

http://merehead.com/blog/best-css-frameworks/

but as long as we're left with a choice, that seems to be the main thing