WHATWG says they're dropping the version number from HTML, and calling the specification a “living document” that will continually evolve without the need for specific version numbers (like “HTML 5”). Like everything else I've seen from WHATWG, this new position reflects reality pretty well, at least for now.

Critics are complaining that a standard should be a complete and consistent target that implementers can aim for, and if there are no version numbers, you can never be sure when you've achieved conformance with the spec, and different browsers that implement different revisions of the spec will be incompatible. However, these people have an idealistic view of how things should work - they have no idea how things actually do work in this field. No browser has ever been 100% compliant with one specific version of the HTML specification; browsers implement whichever bits and pieces of the latest spec that they like best (plus other bits and pieces they made up themselves). Thanks largely to WHATWG's work, this situation has rapidly improved over the last several years, but it will be many more years before the Web is stable enough that trying to implement a particular version of HTML actually becomes useful.

Meanwhile, W3C will still put version numbers on everything. They still cling to the fantasy that someday somebody somewhere will try to implement a spec just because the W3C says they should.