Chris Coyer over at CSS Tricks posted about the possibility of CSS4 (or lack of). In the article, there are quotes from industry folk who say it won't ever be a thing. As the highly acclaimed Justin Bieber movie states, "Never Say Never".
Back when CSS3 was popularized, it forced a lot of folks to talk about CSS and the new specification. It also made it easier for those of us in academia to sell the idea of upgrading our courses.
I hope CSS4 becomes a thing, because when the new spec comes along, I want to be able to justify the changes easily to those who have no idea what CSS is.