Except, if Apple opens up like people want them to, things like payments and especially subscriptions is going to be fragmented all over the place, and I can no longer choose to do all of my purchasing through one store.Then keep doing that. Absolutely nothing in this article is suggesting otherwise.
Just because something is available doesn't mean you have to use it.
I may be a minority, but I have services that I subscribe to through the app store even though it sometimes costs extra, simply because I find it easier, especially when you want to unsubscribe. And, it's easier to get an overview on what I am currently subscribed to.
It will NOT be possible to simply ignore third party app stores and carry on like nothing happened. It will change iPhone into the same sorry mess that is Android and Windows. This is the last thing I want.