Fascinating conversation happening about CSS4 on Github. A lot of very good points both for and against. I already posted my thoughts last week, and it's looking more and more like CSS4 is going to become a thing, despite plenty of good arguments on both sides of the fence.
I still think this won't create anything like the popularity we saw with CSS3, but it doesn't hurt to try. And in any case, I am a firm believer in the power of language. If you want people to talk about something, the best thing you can do is make it easier to talk about, and the rest will follow.