Do you really think that there will be more competition? I fear what will happen is that the big corps will set their own stores to distribute their own apps, and that's pretty much it. The user won't see any difference in pricing. The small dev will be hurt because each store will make less money and will likely implement price increases to compensate.
We don't have to speculate - the desktop OS world has exactly this structure - an open ecosystem with a first party app store that ships with the OS, but the ability for other app stores to exist or even for developers to ship their products independently.
In practice you still see a decent amount of activity on the official app store, along with some other major app stores, and a relatively small amount of independent distribution. There's still a good amount of small independent developers shipping apps (both on the stores and independently), and there's not a ton of evidence of price increases - in fact there's a very large amount of free software being distributed.
Desktop marker and smartphone software markets are very different. There are many more small utility apps for the smartphones for example, while desktop is more open. Discoverability in particular is a huge issue for a small desktop app developer. I don't think comparing to desktop is a good example. On the other hand, desktop app market does illustrate the point I am making — big corporations running their own "stores" to the user disadvantage. And don't let me start about horrible installers that companies like Adobe or Microsoft ship which will change your system configuration and litter your filesystem with random crap.
