Syrenne on Twitter mentioned an angle I didn't consider that makes me kinda hope that there isn't a major innards upgrade for the next model of the Switch. If there is, then that doubles the configurations that need to be QAed on the already many possible use cases of the Switch (docked, handheld, tabletop, etc.).
It's hard to know what Nintendo is thinking, but I expect this new model to be a minor upgrade (screen, battery life) and a cost savings revision.