Continent-scale grids of the scale we need look very unlikely to happen due to regulatory / NIMBY concerns - see the decade long delays for Clean Line Energy to get anything moving. Maybe we'll get a federal administration bold enough to push it through but I wouldn't count on it. That means we'll have to vastly overbuild solar + storage as you said. Luckily the current cost trajectory makes that look possible, but seems worthwhile to have demand side planning in the mix to balance the overbuilding.