Ayer, 28 de octubre de 2014, el W3C publicó HTML5. A vocabulary and associated APIs for HTML and XHTML. W3C Recommendation 28 October 2014, la recomendación final de HTML5.

¿Significa esto que ya se puede utilizar HTML5 sin problemas? No, algo ha cambiado, ya tenemos una versión estable de HTML5, pero eso no significa que de un día para otro todos los navegadores web lo soportaran mágicamente. Los navegadores web actuales, y no digamos los que tienen varios años, no soportan muchas cosas de HTML5, así que se debe utilizar con precaución.

El W3C lo anunció con la nota de prensa HTML5 is a W3C Recommendation:

The HTML Working Group today published HTML5 as W3C Recommendation. This specification defines the fifth major revision of the Hypertext Markup Language (HTML), the format used to build Web pages and applications, and the cornerstone of the Open Web Platform.
“Today we think nothing of watching video and audio natively in the browser, and nothing of running a browser on a phone,” said Tim Berners-Lee, W3C Director. “We expect to be able to share photos, shop, read the news, and look up information anywhere, on any device. Though they remain invisible to most users, HTML5 and the Open Web Platform are driving these growing user expectations.”
HTML5 brings to the Web video and audio tracks without needing plugins; programmatic access to a resolution-dependent bitmap canvas, which is useful for rendering graphs, game graphics, or other visual images on the fly; native support for scalable vector graphics (SVG) and math (MathML); annotations important for East Asian typography (Ruby); features to enable accessibility of rich applications; and much more.
The HTML5 test suite, which includes over 100,000 tests and continues to grow, is strengthening browser interoperability. Learn more about the Test the Web Forward community effort.
With today’s publication of the Recommendation, software implementers benefit from Royalty-Free licensing commitments from over sixty companies under W3C’s Patent Policy. Enabling implementers to use Web technology without payment of royalties is critical to making the Web a platform for innovation.