And what happens at the end of the 3 years? If apps are pulled, are people who downloaded the apps through those alt-stores going to lose access to updates, causing security issues or a support nightmare when the users don't see new features?

We'll see Android users needing to have multiple app stores just to get all the apps they want/need, along with the updates. From a user experience point of view, that sounds worse, even if the competition is meant to make things better.