A few years ago I thought that XHTML would eventually be widely used but when the W3C decided to standardize on HTML5 (which I love for non Semantic Web reasons), that may have been the beginning of the end for RDFa because RDFa is an XML application.
I believe that a better alternative in a HTML5 world is to keep RDF separate from web pages but have a clear set of rules for finding RDF data files that correspond to web pages (either static or generated). One rule might be to look for a file named index.rdf for top level domain URLs; for example, see if http://markwatson.com/index.rdf exists for http://markwatson.com. For a URL like http://markwatson.com/hobbies look for http://markwatson.com/hobbies.rdf or http://markwatson.com/hobbies/index.rdf.
Although CMS support (e.g., Drupal) for RDFa and helper libraries like the RDFa Rails plugin might make it fairly easy for some web sites to provide RDFa, I think that we need something simpler that might be adopted by more web sites.
I am writing an open source tool (that will be an example program in the Semantic Web book I am writing) that will generate RDF data from web pages. I’ll post a link when the code is ready.