I guess we don’t say that USA had “sanctions” against the Soviet Union, but there was a monumental improvement in economic relations after the Soviet Union collapsed, no? So we have a direct example from history from the same region.

I would say that Vietnam also shows that economic relations can improve a lot even without a fundamental change in the regime.

China is also an example where economic relations improved.

I don’t see any reason to think that sanctions can’t be lifted. But it may require a complete collapse of Putins regime/party for it to happen on a short timescale. Is there any reason to think USA wouldn’t be willing to open up to a new leadership if they have a radically different attitude and pull out of Ukraine?

If Russia turns into something like North Korea or Iran, then yeah, the outlook is not good. But why should it be?

From a game theoretical point of view: I don’t think any leader of any country wants to end up like North Korea, so the precedent being set is good.