I am sure they will be able to find ways to either circumvent that or find ways to make money.
For example, lets say the bill goes through. Most likely, a store like EGS won't come pre-installed on Playstation and the user has to go out to their website and install it. Now I'd say that's already quite a lot of console users that won't go out and install other stores. But on top of that, I am sure to develop on a closed platform like Playstation, you would still need Sonys approval regardless of whether you publish on Playstation Store or some other store.
So Sony could add in a clause similar to what Valve does with Steam where if you want to publish a game on Playstation, you cannot have the MSRP be lower on any other store on Playstation. So if a game dev wants to put a game on Playstation Store for $20, they can't release the game on EGS for $15. And at that point, I think most people wouldn't even install another store.
So I wouldn't be too worried.
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