If the 12400F maintains current pricing and DDR4 works on the cheaper boards and it beats a 5600X then it's hard to see where AMD will go other than having to massively cut prices.
You could say that about the 11400F vs the 3600, but that's not what is happening despite every major reviewer pushing the 11400F as the best budget option, which i agree with BTW.
I don't know why that is, what i do know is the 3600 is always available despite being more expensive than the 10400F / 11400F and selling in sick numbers while the 10400F and 11400F are quite often out of stock, i think that's because Intel deliberately don't make enough of them, they are a business and having a CPU that's pretty much the same as another CPU in your range $100 more expensive is not good for business, if you keep up with demand for them all you're doing is giving away $100 with every sale of them.