In any event, PMI expects to use the rest of 2011 in a pilot program leading to any initial class of certificate holders by the Q4 of 2011. They've set up a FAQ, and of course there is a PMI Agile Community of Practice.
Why now? Why from PMI. From their literature, PMI says their marketing research of the project management community shows the growing importance of Agile methods to the software development project management community, and they feel this community can benefit from the certification process and from the networking and power of the community that they can establish.