iOS 6's built in Maps app will no longer call on Google Maps as its back end, but will instead host an Apple-made solution. Map's will retain a Street View-style option and 3D building functionality thanks to their acquisition of C3 Technologies, with other mapping data coming from Placebase and Poly9. The design will be similar to the current Maps app, with a minor icon tweak, but will offer a "cleaner, faster, and more reliable experience". This according to 9to5Mac's Mark Gurman, and confirmed by our sources.
Apple has already started to ditch Google Map data in iPhoto, so this isn't exactly a huge surprise.
We're expecting to out first glimpse of iOS 6 and hopefully some confirmation of that Google Maps is gone at WWDC this summer.