Preview at WWDC likely in June, followed by September launch.
Apple's 3D Maps and Imagery See Incremental Improvements
While improvements have been ongoing, MacRumors forum members yesterday began noticing what appears to be a larger set of additions to the 3D content in the Maps app, including both the satellite/aerial imagery and the standard maps. One region that was among the first to be noticed was the New York City area, with a number of improvements including new 3D imagery of the Statue of Liberty being seen.
Old (left) and new (right) Flyover images of the Statue of Liberty
We've also heard from users who have experienced new Flyover imagery showing up in Honolulu, Hawaii and in the San Fernando Valley in the Los Angeles area. The changes are also affecting the standard vector-based maps as well, with users reporting new 3D buildings showing up in New York City and London.
Interestingly, not all users are seeing the new imagery, with some even doing side-by-side comparisons between devices with different results. The difference is presumably due to aggressive caching of maps and imagery, and users who are not yet seeing the new imagery should see updates in the relatively near future.