Apple didn't reveal the feature during WWDC last week, which means that while it was worked on, and is probably still being perfected by in-house developers, we probably won't see this feature until iOS 8.1 at the earliest.
There is some speculation that a plethora of new features for Apple Maps was skipped over because of personnel issues. Some have blamed now departed Maps Quality lead Cathy Edwards, who apparently clashed with several developers. Besides the parked car capability, Apple was apparently hoping to show off new features for Apple Maps related to public transit, and improved data.
Images found in the iOS 8 version of Apple Maps reveals that in the future, the app will help you find your parked car
source: 9to5Mac (1), (2)