Sure. I've been hearing that for 20 years and I sincerely, eagerly and in good faith welcome their arrival.
However, until then, we have to go off of the existing historical reality. We can't run the numbers with any kind of integrity based on what is currently vaporware.
Designs that are actually operating and producing power are not vaporware. The reasons those designs aren't already doing that in the US are political, not technical.
Anti-nuclear politics in the US has made people believe that every nuclear reactor is a Chernobyl waiting to happen. That was a pernicious lie even in the 1980s, and it is much, much more of a pernicious lie now. In terms of the fairest measurement, which is harm done per unit of energy generated, nuclear power, even with reactors of traditional designs, is orders of magnitude better than any other energy source, including renewables, which in turn are significantly better than oil and coal (coal is by far the worst). And with newer designs, not vaporware but actually operating today, that risk per unit of energy generated is even lower.
A sane US government policy would have had nuclear displacing oil and coal starting in the 1970s, as France and Japan did, and reprocessing the waste instead of beating ourselves over the head with a baseball bat by saying the only option was to store it for 100,000 years, which of course is not practically possible. Then we could have a meaningful conversation about how much of that nuclear base load capacity it makes sense to transition to renewables. Plus, if you really think CO2 emissions are a planetary emergency (I personally don't, but GND advocates do), there would be decades worth of CO2 emissions that the US would not have made at all. Not to mention decades worth of coal still in the ground where it belongs, and oil that could have been used for things much more productive than burning it for energy.
You say we have to go off of the "existing historical reality", and while it's true that we didn't do all those sane things in the past when we should have, that still is no argument for not doing them now. We have an obvious alternative source of base load power that would free us from oil and coal staring us in the face, and instead we're noodling about renewables that can't possibly meet the same demand requirements. That doesn't make sense to me.
Sure, you could handwave the "mass societal pushback" and change it to "cheering societal acceptance" and then fudge away the costs associated, but that's simply not what is going to happen.
You have to account for greenpeace and all the organized opposition. You have to account for the politics
That's why you need to go off of concrete material historical reality - if you're free to apply counterfactuals as you please than practically any conclusion is permissible because we can tweak and modify whatever we need.
Just like the "business as usual" advocates are hypothesizing a globally deployable massive carbon sucking technology to somehow exist in the future without a shred of evidence that it's at all plausible. It's extremely dubious gambling with the future of society.
Reality overrides counterfactual hypotheticals every time. When ambitious next-generation nuclear is ready to go, then there's a possible opening but right now it's simply not there.
However, until then, we have to go off of the existing historical reality. We can't run the numbers with any kind of integrity based on what is currently vaporware.