I think this is their "extensive beta and data collection period". Just using the entire iOS 6 customer base as the experimental set.

I think it would be kinda cool if they'd push the new maps as an app available for iOS 5, and if Google had their native iOS maps app ready, and the transition weren't so abrupt. I realize the mapping subsystem is baked in more deeply, with various APIs and libraries available to all apps on the system, not just a standalone app, but it would still be helpful to have the standalone apps. (If Apple Maps were available as a standalone app, that would facilitiate the "extensive beta period" you suggested without all the ire that they've attracted this way; and I really hope that Google Maps is coming back to iOS at some point real soon now.)