Exactly.
And what about support for older devices that won't run ios6?
Well, those devices would be running the Maps app from the older iOS version, and thus connecting to Google Maps.
Remember, this doesn't mean that Apple intends to block Google Maps. It just means that the built-in Maps app on iOS 6 (and later, presumably) would access a different map database.
If someone builds an app that connects to Google Maps, that's fine.
Another option is for Apple to make their own map service the default on iOS 6, but offer Google Maps as an alternate data source, just like one can choose between Google, Yahoo, and Bing as the default search engine for Safari.
What practical advantage does this switch give me, the user?
We don't know yet. Hopefully better data, although right now, it seems difficult to imagine that Apple could beat Google at mapping services. In particular, Google has a several year head start on Apple concerning Street View.
About a week ago, I saw am unmarked street view surveying car not far from where I live. Was it Apple's? Who knows.