This infrographics shows how HTML5 First draft evolved in 2009 and how HTML5 is gaining momentum in almost every web based projects. Let it be mobile game development, responsive layout, muti file upload (flickr came with this concept using HTML5.
How easy to embed audio, video tags and email address, date validation in in-built now. In short you can't live without HTML5 in near future. So better learn it 🙂