I think there's no one could be as professional as a moderator/ beta tester. So I just take what he said as a truth. Maybe he just made a joke, or he can come here and say " yes, I'm joking", and we stop this topic, right?
Good thinking with some mistakes.
1-Absolutely, DX12 only comes with Win10 and DX12 capable Video Card. But that not means you have to buy a new card like GTX980Ti (Maxwell 2.0), or a R9 380 (GCN 1.2). Almost ALL THESE current DX11 capable cards are capable with DX12 except HD6000, HD5000 and intel 3rd ones.
2-just as J Van E said, P3D has various DX version capability. My friend had a GT240 which could only capable with DX10, but he could also use P3D 2.5, but run in DX9. So, you know, the OS is not that serious, and P3DV3 mostly will also remain DX11 support for old systems.
Er...right, home simmers are not LM's priority, never will be. But look at the route map from P3DV1 (DX10), P3DV2 (DX11), and possible P3DV3 with DX12. Each version update came with DX version update. Maybe V3 will not initially support DX12, but it nearly 100% will in the near 3.1, 3.2 etc. Personally, I think LM is quite aggresive in obtaining performance for their simulator.
Maybe, we all make speculations.