HTML5 is about to rock our world. There are books written about why that is the case, but simply put, it can provide a much better user experience on both desktop and mobile devices, and could lead to a convergence between native applications and the mobile web.
I believe in HTML5 enough that I wanted to make it one of the top 5 initiatives for Drupal 8; and switch Drupal's default doctype from XHTML to HTML5. This is the fifth official Drupal 8 initiative after the Configuration Management, Design, Web Services and Multilingual initiatives.
I have asked Jacine Luisi to be the Initiative Owner for the Drupal 8 HTML5 Initiative. Jacine is a prolific themer and contributor known to be a markup/CSS nut. I'd also like to recognize Jen Simmons for all her evangelism work on HTML5 in Drupal. I hope that work continues as it can feed into the HTML5 Core Initiative.
The way we'll approach this initiative is by starting off with some of the low-hanging fruit, and gradually work our way up to more advanced parts of the specification. In her announcement blog post, Jacine provides a plan for what that means.