Caporegime
Exactly, can't have it both ways, this is an Intel like trick however 'some' people may want to spin it. I got my x470 board on the assumption that it would be sorted to ryzen 4000, after all, AMD led me to believe that to be the case with the AM4 lifecycle crap.
Some may argue I've been naive to think that, but if AMD didn't know at the time fair enough. If they did however, it's clear deception, as they could have just said there and then 1st and second gen won't support 4000 series CPU. The fact they are saying rom size is the limiting factor, it's clearly intentional they don't want to support, not can't. The MSI max board's and most high end x470 have large enough rom capacity as well as capable enough vrms.
They will likely u-turn to partial support, but either way I'd like the option of using ryzen 4000, but likely would stick with the 3900x as it does perfectly fine and will likely age well.
You have a good motherboard which wasn't cheap,and I have a £140+ B450I Strix mini-ITX motherboard(32MB BIOS chip),and AMD mini-ITX motherboards are a bit pricey. It's rather annoying,but I feel sorry the most for the people who bought a B450 after Zen2 was launched,and now are faced with a one generation motherboard. I suppose at least I started with a Ryzen 5 2600 back in 2018,so had at least I have one generation of upgrades,but I was surprised that the B550 was AWOL for so long.
Hopefully they reevaluate this and change their position, they did with the 3000 series not being x300 series compatible. It honestly seems like very flimsy reasoning and makes Intel's claims of pinout changing seem more legit being a supposed hardware change.
Having to buy a new motherboard isnt the end of the world, just I'd prefer to drop in a cpu rather than take out an old motherboard and put in a new one.
It depends if they believe that Zen3 is good enough,that they can just ignore annoyed B450 and X470 owners and forge forward. This is the problem,these companies act nice when it suits there.