Most countries and business want to do something with their earnings. If you get paid in rubles for your oil, then you can only buy things denominated in rubles

Most countries and business want to do something with their earnings. If you get paid in rubles for your oil, then you can only buy things denominated in rubles. If your general trade is collapsing, this isn't such a bad thing - you need to make an increasing proportion of your consumption. But if you retain an economy that wants to do general trade, you will probably want something other countries accept. So although it is possible that "we'll see the dominance of the USD erode in the next three decades", it is much less likely that "commodities [in general would] be priced in local currencies of the producing nations [following the example of Putin's Russia]". The problem with your prediction though is that it's boring - it's too easy to be true as phrased. For instance, if we see a new cold war divide into a China-focused world and a US-focused world, then the growth of whatever currency the China-focused world uses will necessarily result in decreased USD dominance. Or if not China, then India. Or who knows who. Or maybe the US will descend into civil war and someone else will pick up the mantle of world hegemon. Or the US will amicably divorce, and the Floridollar will dominate international trades. So it's more likely that you'll be right for the wrong reason, than that you'll be right for the reasoning established in your post.