The only change is that Mozilla isn't funding new feature development in Persona this year since Firefox OS has slightly more time-sensitive / urgent needs. Persona is still actively supported by Mozilla, and is a critical part of our own infrastructure.
Persona ain't going away so long as we're still relying on it.
I'm not sure what the long-term plan will end up being. I personally hope it can find a new direction to grow eventually. (Note: I'm a Mozilla developer but I don't work on Persona or Firefox Accounts.) We use Persona extensively for our own sites and tools, so I'm sure there would be some sort of migration process if Persona were ever shut down in favor of some replacement.
In hindsight we did indeed spend too much time experimenting and tweaking, and not enough time saying "it's good enough" and driving it to completion.
But it's open source :) we're still working on getting it there. The next release will dramatically scale back the API complexity, lock in the APIs and data formats, and pave the way for native browser extensions, self-hosted polyfills, etc.
