For Drupal 8 we're planning to split the RDF module into two decoupled modules:

The RDF module will only care about defining the mappings with the entity types and the fields, without dealing with any syntax/presentation. Thus it won't do much on its own, but other modules can rely on it to output data.

The RDFa pieces of the existing D7 RDF module will be moved into a new module that relies on the RDF module to get the term mappings and constructs the RDFa markup from these mappings.

The term mapping of the RDF module needs to be refactored to take advantage of the new Entity Field API and improved. A lot of thinking went into this issue already, and I'm sponsoring Lin Clark to work on that after DrupalCon and drive the issue home.

The rest of the work involves the second module which will inject RDFa markup in HTML. This module will have to plug into our new theme layer: Twig. Given how much we will use Twig, we need to first get familiar with it. Twig is not completely integrated in core, which is a blocker for us, so let's help the Twig team to finish the conversion of all the file templates and theme functions. On Friday, a few of us will join the Twig code sprint at the DrupalCon venue. We only have 5 weeks to go before code freeze, join us if you're around!

Remote participation is also possible, all the documentation and links to issues about Twig are there: https://drupal.org/sandbox/pixelmord/1750250