Earlier quoted context omitted.
If Microsoft were to shut down the other channels, that would be true. However, nothing stops you from making a traditional windows app. It just won't run with the Metro UI.
Which is barely a defense: Metro is the future of Windows applications and I doubt users will be very excited about their ability to install "traditional" apps. I'm surprised that Microsoft beat Apple to locking down their desktop OS in the style of iOS, but in either case this is extremely disturbing.
If you really must distribute an app that needs to go outside of these walls non-metro apps are perfectly fine. You can accomplish a lot of what Metro apps can do today outside of Metro (at least from a look and feel perspective). And as Apple has noted, there is the web too.
I personally like the fact that you now have a CHOICE of where you get your apps. A curated app store, the old wild west of native apps, or the web. Choice is good.