Yeah while more cores is likely sensible for future performance headroom, OP did ask for “minimum CPU/GPU” for 4K, and the extra cost of a 59x0 isn’t going to buy you any more performance at the moment. The 5600 also comes with a stock cooler, whereas the higher models don’t, so there’s another saving there too.
I too would hope that DX12 will bring performance improvements for the reasons you say, but Asobo have been pretty clear that they are going DX12 for the added graphics effects it opens up to them (and Xbox), not for performance reasons (though I don’t think they have said that it won’t bring a boost).
As for GPUs, here are some more stats from Linus:
I’ve not looked too closely at the new AMD GPUs, but if it were my money, right now, I’d go with a 5600X + RTX 3080 + 32GB. You can always upgrade the CPU later if the sim starts to make use of more cores in the future.