The HTML Working Group—which is chartered until 31 December 2004 [Note: The charter itself was last modified, January 9, 2003.]—has an Activity Statement.
And, from The HTML Activity Statement, we find,
“HTML is the family name for the group of languages that form the lingua franca of the World Wide Web. The HTML Working Group is chartered to evolve HTML into an XML-based markup, modularize it to make it easier to combine with other markup languages, and correct the problems known still to exist in areas such as internationalization, accessibility, device independence and forms processing.”
There appears to be a State of Reluctance about serving all sites as XML. Some sites which were written as XHTML 1.0/Transitional have been revised as Strict. Not XHTML 1.1. Not XHTML 1.1 + XML 1.0. Perhaps, they’re served server-side.
And, some famous sites still languish as XHTML 1.0/Transitional!
Perhaps, after May First, all redesigned/rebooted sites will be Strict.
Or, HTML 4.01.
No evolution by Anne van Kesteren was published November 22, 2004. He concluded it, “Now, we are using HTML again.”
Roger Johansson published The perils of using XHTML properly on January 18, 2005 and included these lines “When I decided to start serving XHTML as application/xhtml+xml to capable browsers, it would have saved me some headaches if I had known about an article like this to read before making that decision. I might even have considered using HTML 4.01 Strict instead.” He did so. Choosing HTML or XHTML [November 4, 2005].
Even W3C®’s HTML 4.01 Specification uses HTML 4.01/Transitional.
Some other sites I visit are served as HTML. Cloudal Partners, Juicy Studio, Meyerweb and Robert’s Talk. And, then there’s, Bite Sized Standards which appeared in April  (and may have required John Oxton’s tacit approval of using HTML. Or, James John Malcolm simply did it). There may be other websites but I haven't found them.
As I've written elsewhere on this site, this site and others we develop are 4.01/Strict. Previously, they were XHTML 1.0/Strict but that changed in early 2005 for various reasons. One reason I've stated, “HTML 5 purports backwards compatibility” is disingenuous: HTML Working Group Roadmap [Note: The URL doesn’t have HTML but XHTML-Roadmap.] and W3C Technical Reports and Publications make no reference to an HTML 5 working draft, candidate recommendation or recommendation. (It’s not found in ‘Working Drafts no longer in development’, either.)
HTML 5 notwithstanding, I’m curious to know if there could be further unheralded abandonment of XHTML.
I guess we’ll have to wait and see what after effects May Day brings.