FWIW
I have a 5900X so not sure it would be worth the swap. At least until I see significant, and applicable, reviews.
My PC is really just an expensive game-console, with a boat-load of peripherals attached; the power needed to browse the net; watch videos; etc, is well below even a modest sim rig.
This sounds like a good trend, for PC simulation anyway.
Related YT video:
I’m greedily looking at the X3D because I have the need for more speed. If I dive in I would be migrating from a 3700X. The numbers look promising but I’m not sure if I can justify the extra cost. I may settle for the 5800X and call it a day. Decisions, decisions…
Don’t settle for a different Ryzen 5000. If the cost is too high, just wait till it gets cheaper. It is in a different league than non-3D cache processors for simulators.
As a 5800X owner, I concur. The 5800X runs too hot as it is. It ain’t bad, but it ain’t a motherlovin’ 5800X3D! 
That CPU is unbelievable.