dyson doesn't sell third party stuff. If ikea was forced to sell all their chairs at every store, but only for 3 years. are people looking for chairs going to have better options for where to get chairs at the end of the 3 years? I think they'll just be confused and go to their previous buying habits (namely their favorite furniture store or google/epic/samsung app stores). I expect a mess with a lot of unintended consequences, such as conditioning people to think all third party app stores are the exact same, which could harm distribution methods like fdroid (though epic might be happy with that type of outcome)

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.

Are devs going to be forced to support all the app stores too? Will they need to go through N separate registrations, N separate support processes?

I can see a good number of devs going “eeuuuggghhhhh” and just letting an app rot, just only publishing to one store, rules-be damned, or just going to iOS.

Will devs be forced to make accounts on all the stores in order to collect earnings from sales on that store? Are stores opt in or opt out from a developer pov?

Google can’t force them to use Google for payments anymore. Maybe the multiple stores will force developers to integrate their own payment processing that can be used across all the stores, because it won’t be tied to any of them.

Their local store surviving and expanding their operation during these 3 years could be enough of a benefit.

The store can plan for what they'll do 3 years later, so progressively injecting IKEA competitors in the mix and getting people to know the other options could lead to a durable business. Especially if IKEA loses enough sales that they'd want to keep selling their goods in third party stores to keep shelf space from competition.

To get out of the metaphor: if alternative app stores become big enough to thrive on their own from this initiative, app makers will keep pushing their apps other there. In particular this whole scheme assumes some level of compatibility, so the burden should be light enough.