And this quote by Hixie: "You know what will be around ten years from now by looking at what is implemented in two browsers today. If it’s implemented in two browsers today, I can almost guarantee it’ll still be around in ten years. If it’s not, all bets are off. This has nothing to do with “living standard” vs. versioned specs, though. HTML4 has all kinds of features that aren’t in HTML anymore — for example, <object declare> and <a coords>." (http://html5doctor.com/interview-with-ian-hickson-html-edito...)
See also the FAQ: https://wiki.whatwg.org/wiki/FAQ#What_does_.22Living_Standar...
And this quote by Hixie: "You know what will be around ten years from now by looking at what is implemented in two browsers today. If it’s implemented in two browsers today, I can almost guarantee it’ll still be around in ten years. If it’s not, all bets are off. This has nothing to do with “living standard” vs. versioned specs, though. HTML4 has all kinds of features that aren’t in HTML anymore — for example, <object declare> and <a coords>." (http://html5doctor.com/interview-with-ian-hickson-html-edito...)