So what, they still can't just upload all apps from the Google Play Store into their own.
I've actually tried some of the other stores for publishing my own apps and my experience is that users of those alternative stores either have no money or do not want to spend any money on apps. (the sales have been catastrophic, even in Amazons App store)
The point of an app store is to make money for the app store owner. The owner charges "rent" to put your app in its store. The rent is a cut of your earnings. So, given this fact - do you think putting Google Play on its Tizen would benefit Samsung? Because then the marketplace would still be google's and the revenue would still be theirs..
Amazon Marketplace is not Google play is it? So the revenue from it is going to amazon.