Any time I look at the new features in Chrome, I ask myself, "whose actually using this stuff?". Even though Firefox usually keeps pace pretty well it's pretty common for implementations to differ, and thus you're on the hook for browser quirk issues in any new feature you adopt immediately. Not to mention I've always had the anchor that is IE to temper any hastiness to use a feature (even if you simply don't implement the feature for IE, that's still an extra error state to handle unless you're willing to drop IE support altogether).
It can't even be 1% of websites out there embracing this stuff. I'm guessing the biggest consumer for most of the new features in Chrome is probably Google web developers. There's quite a lot of things that only end up half implemented, too.
Although the RFC these days seems to just be a design spec doc for Google, I suspect you could carve it down to less than half of what it is and render 99.9% of websites out there just fine.