They have closed up P12 development and moved on to unimesh Poser. So P12 will be the first version to go straight from early access to final version. Personally, I don't think they could make unimesh an update for P12 because it's a whole different code base from ground up. That was also why it was not worth investing time on fixing some issues, because they would have to redo them in unimesh Poser anyway, or in some cases, they would no longer be an issue once unimesh is in place.
I totally agree that they should close P12 as it is, and get into unimesh Poser, because it will take time, and patience is running thin. It was important that they have spent the time to fix all these issues with P12, so we have a more usable version until unimesh Poser comes up. Unimesh will open a lot of doors that have been closed to Poser until now. If they keep working on P12, it will never happen (not enough programmers). So AFAIK, unimesh Poser development has finally started. There was a lot of planning until now because this will significantly change how Poser works inside.
I had originally predicted unimesh Poser would be out this year, but I forgot they were still working in P12, and that a change of this magnitude would require substantial planning before they start doing it. Being a software developer myself, I know how important the planning phase is. So for now, it's P11 and 12.