I wasn't aware of that. Won't it be living hell for web developers trying to build cross-browser compatible websites? Will you have to perpetually keep track of the implementation status of every HTML5 features for every browser in addition to keeping track of every browser version and their market share?
Edit: I wasn't referring to the DOCTYPE. I was referring to the fact that up until now you could just assume it was safe to use HTML 4.01 because you knew it was implemented (almost) consistently across a large share of browsers out there. Now you will have to keep track of features individually instead of keeping track of a discrete set of features AKA a HTML version.
The doctype has never been useful for detecting browser features. You needed, and still need to, do that with user agent sniffing or with Javascript. All the doctype has ever been useful for is for controlling the browser rendering mode, i.e. standards compliant mode or quirks mode. HTML5 defines much more precisely how pages should be rendered, including how to render broken HTML pages, thereby obsoleting a thing like quirks mode.
"The next version of HTML doesn't have a name yet. In fact, it may never have a name, because the working group is switching to an unversioned development model. Various parts of the specification will be at varying degrees of stability, as noted in each section. But if all goes according to plan, there will never be One Big Cutoff that is frozen in time and dubbed "HTML6." HTML is an unbroken line stretching back almost two decades, and version numbers are a vestige of an older development model for standards that never really matched reality very well anyway. HTML5 is so last week."
Check out http://www.modernizr.com, for example, which abstracts feature detection for many advanced "HTML5" features. You (sorta) don't have to worry about browser version, you just have to worry about feature support.
Feature detection is a far easier strategy for development than user agent sniffing, in my opinion at least. Granted it's less helpful for CSS-related issues, which more have to do with inconsistent implementation than with whether a feature is or is not supported.
Edit: I wasn't referring to the DOCTYPE. I was referring to the fact that up until now you could just assume it was safe to use HTML 4.01 because you knew it was implemented (almost) consistently across a large share of browsers out there. Now you will have to keep track of features individually instead of keeping track of a discrete set of features AKA a HTML version.