HTML 5.1 is now a W3C proposed recommendation, and the comment period has closed. If no major issues have turned up, it may become a recommendation soon, susperseding HTML 5.0.
Browsers already support a large part of what it includes, so a discussion of its “new” features will cover ones that people already thought were a part of HTML5. The implementations of HTML are usually ahead of the official documents, with heavy reliance on working drafts in spite of all the disclaimers. Things like the
picture element are already familiar, even though they aren’t in the 5.0 specification.
There’s already a working draft for HTML 5.2. The Web Platform Working Group is aiming to produce a recommendation in late 2017. The changes listed so far appear minor. Other changes are under consideration.
The development of the HTML language has become a continuous process, so W3C recommendations are markers rather than points of sudden change. Still, they’re worth keeping track of.