Yes, this is big achievement for a content management software to be WCAG complaint! We love Word Press for several years now and one of the main reasons for that is its ease of use. Now we love it more because now WordPress goes WCAG; thanks to the dedicated efforts by wonderful Accessibility team at Word Press and community that helps.
Here is what Rian Riatveld wrote in the recent announcement:
All new or updated code released into WordPress core and bundled themes must conform with the WCAG 2.0 guidelines at level AA.
There are also many theme authors who are putting in great efforts to code accessible themes and there are several plugin authors who are doing their bit as well.
Proud of Word Press team and we are sure, it would not be possible without support from everyone working on Word Press. Thanks all. Hope authors / vendors of all other content management software would inspire by effort of Word Press and sign-up to build accessible software.
Way to go!