If they make an X570-equivalent, but cheaper, then why does B550 exist?
If they were to make something 'better' than X570, how would it be better in a way that matters?
Even the occasional X370 board that wasn't poorly designed can handle the current 3000-series CPUs; most of what AMD has accomplished with successive chipset releases, it seems, has been to assert a near-Intel level of control over their board partners with respect to design and QA.
As it stands, X570 seems to be a in a pretty good spot with respect to having a competitive featureset and quality implementations. I can't really see a path to needing a replacement without first making significant changes to the CPU platform, mostly to the tune of even more PCIe lanes for stuff like NVMe and USB4 / Thunderbolt.
X570 is extremely expensive. As expensive, if not more expensive even than its Intel counterparts from what I'm told. B550 exists to create a cheaper option for motherboard makers and thus, consumers. However, 550 is not only a lower cost chipset, but it's also a lower end chipset. There is some crossover, but they represent different segments in the market. Therefore, there is still room to make X570 cheaper than it is. It is both costly to manufacture, and its power hungry. As for making something better in a way that matters, I mean expanding the feature set or moving technology forward in some way. Whatever form that takes.
There are probably multiple reasons why we aren't seeing a new chipset for Zen 3. A new chipset might not be ready in time for the release. There might be delays on ASMedia's part since it's unlikely AMD would try and do another one in house. It could also simply be that AMD saw insufficient gains from such a project at this time. That is, they won't see enough ROI to bother with it given that a theoretical X670 chipset will be the end of the line for AM4. Fewer people are going to want to buy into a new chipset that will have such a short shelf life and really doesn't bring anything new to the table in terms of features or performance. And, as I said,
(and you just said) X570 is well positioned in terms of its feature set.
One thing you have to consider is that it isn't necessarily the end users that ask for innovation. Often, it's the motherboard manufacturers themselves. Those are AMD's customers as well. I'm sure MSI, GIGABYTE, ASUS, ASRock and more would like X570 to cost less and use less power so they could ditch the active cooling on X570 motherboards. Again, there is room to make X570 cost less and it would improve margins on higher end motherboards. Right now, motherboard margins are razor thin pretty much across the entire product stack.
Lastly, us not seeing a need for a new chipset has nothing to do with anything. We rarely need new chipsets, but usually get them anyway. Intel has done it more times than I can count. Sometimes, it's feature set doesn't even expand. It's just rebranded and that's it. AMD has done it too. A520 isn't much if any different from A320. 990FX was identical to 890FX. The only difference was a VRM specifications update and support for one additional C-state that Bulldozer CPU's supported that older Phenom II's didn't. But the chipset silicon was basically the same.
