They're not going to be putting the play store on there for the same reason amazon doesn't put it on the fire - their model is to provide the payment/content ecosystem for the ol' 70/30 split.
On a perfect world, they'd get a special partnership with google to get an extra OUYA tab to the play store. For OUYA dedicated games, which would show on OUYA devices and pay OUYA developers with that. Even if google would sacrifice their 30% for it. It still seems like this would be the ideal deal for all parties: users, developers, google and ouya.
