There are already at least two threads on this topic, but given them that one has devolved into an argument over the reasons for the end of DSON compatibility in Poser 12, I decided to create a separate one focused on exploring solutions and work-arounds.

I can confirm my suspicions that you can technically get G8 figures into Poser 12 via the following steps:

1. Load your DSON-converted figure into Poser 11
2. Turn DSON subdivision off (Scripts >> DSON Support >> Subdivision >> Subdivision OFF).
3. Re-save the figure in your Poser library.
4. Load the raw figure geometry (OBJ file) into Poser 12
5. Go to the Setup Room and make your libraries visible (Window >> Libraries)
6. With the imported OBJ selected, load your re-saved figure from the host library..
7. Scroll to the bottom of the body part list that appears and uncheck "SubD."
8. Click OK to proceed with the rig and morph transfer.
9. Return to the Pose Room.
10. Change the skinning method on the new figure to Poser Unimesh (Figure >> Skinning Method >> Poser Unimesh).
11. In the Properties palette, subdivide as desired.

I assume this process will work for G1-3 figures as well. This will at least get a posable, morphable, and subdivided Genesis+ base figure into Poser 12. The downside is that I doubt the "Transfer Active Morphs" script will work on this converted figure, so getting clothes to fit a morphed character won't be as simple as it once was, though it's still technically possible via a process similar to the above. Pose presets are also unlikely to work.

I have some background in programming, and I've been researching ways to convert Python 2 material to Python 3. While script conversion seems rather easy, I think the core of the incompatibility lies in the "dzdsonimporter" PYD file, which is a compiled module. This means that I would most likely need access to the source code. Given that Daz does not appear to have any plans to continue supporting (and thus profiting from) the DSON Importer, what do you think the chances are that they'd be willing to open up the source code? Does anyone think it's worth asking?