Based on my crawler runs, there is a LOT of XHTML 1.0 on the web and a modest amount of 1.1
The XHTML 2.0 group at W3C ground to an end as HTML5 picked up steam and was finally formally closed last December after years of inactivity. The obvious intent is that people interested in XHTML will use HTML5 output as formal XML.
From the recommendations:
When HTML5 is serialized as a valid XML document, it will be called XHTML5. Any page served as XHTML5 must have a media type specifying XML such as "application/xhtml+xml".