Well, Zope moved onwards from PAS to PAU and I think Plone should too, because:
It seems like just yesterday that PAS offered the promise of being the nice clean way forward for authentication, and even offered a path to Zope3. I've been subscribed to zope-dev since then, but somehow the anointing of PUA escaped my attention. It seems like plenty of people in these -dev communities aren't aware the world has shifted again under them, so I pity the poor soul who attempts to use/install/configure this software.
I am writing a PlonePAS plugin, that makes the world of PAU available to Plone
Hopefully you will finish by the time PAU is considered ugly/unpythonic/whatever enough to replace <wink/sigh> The sands constantly shifting under our feet sounds like a much bigger problem than whatever was wrong with PAS, or whatever will be decided is wrong with PUA (and repeat ad-nauseam for the variety of successors.) Mark