For me it's definitely a very plausible option.
My platform is still good old FSX Acceleration (No P3d) and for me 2020 was always the time for a new sim and my pc will also be 4 years old by then.
I'm signed up for the insider program and very curious to see how it'll perform on my aging machine.
I highly doubt PF3 will still work out of the box, because I think they will present a new or largely new SDK if they change the AI behavior and I fully expect them to optimize AI, one of the points where simmers in FSX invest lots of time to fix it up

. We'll see.
Definitely curious to find out more too.