Which entails continuing to put games on Switch for the foreseeable future, but it doesn't entail the two having almost the same first-party library for the successor's initial years. Having very few exclusives is going to impede the migration, not help it. Because as much as retaining the Switch install base is a goal, so is actually moving them to the Switch 2.
Moving to the next thing because it's the next thing is only going to be so effective, games you can't play elsewhere need to be present as well.