Not really, the economics are just better for the platform with vendor lock-in. They'd still recoup their costs via their store, which they can gift powerful advantages like making it default, having it be more integrated in various ways, etc. It would likely end up as a power-law distribution of store usage with the platform owner on top, so platforms would still make their profits. Having an option for another store wouldn't be the end of anything, and would improve consumer agency significantly.
The lethal threat to fully unlocked consoles with no contractual limits ruled out by law isn't other stores or even piracy. It's people realizing that if they're selling the hardware at a loss, it'll likely be the most cost efficient GPU compute you can buy. This isn't supposition, it happened with the PS3: https://www.theverge.com/2019/12/3/20984028/playstation-supe...
There are jailbreaks for the PS4, and it seems more likely than not that there will also be jailbreaks for the PS5. The barriers for actors who want to exploit console compute power are not significant. But they are significant for regular consumers.
Building cluster out of machines you’re not sure you’ll be able to consistently jailbreak and therefore replace even in the near term is a huge barrier to building a PS4 cluster like the PS3 ones.