At this point the W3C is basically under control of Google anyway.
Chrome, Chrome, Chrome, and Chrome?
Ironically, Apple's walled garden is the last thing standing between Google and total web dominance.
A CSS issue is not going to break any site unless it causes interactive elements to overlap or be hidden from view. Most sites do not implement bleeding-edge features for this reason. Those that want to set it up will do it in such a way that there's a fallback for browsers that don't support that function.