The team has been focused on Persona support in Firefox OS, the Firefox Accounts stuff which relies on some of the same code as Persona, and integration on Firefox desktop. They have by no means stopped working on Persona, but resources on the Identity team seem kind of limited relative to how much there is still to be done.
Hmm, right. It seems that interest has died down a bit, so maybe it'd be worth spending some man-hours keeping it alive, even if it takes away from development time. The community could maybe help with development? If not with Firefox OS/Accounts, at least with the web component.