part of Android L for phones.Parental controls have been something that Google has mostly left up to 3rd party developers. It wasn't until Android 4.3 that Google added anything close to parental controls with the restricted profiles, which would allow control over what apps could be accessed. Unfortunately, restricted profiles are part of the multi-user system, which is currently only available on Android tablets, though it has been rumored to be a
Whatever changes Google has planned will undoubtedly affect Android apps for Google services, but there is no timetable given for the kid's versions of these apps. So, there is no guarantee that it will happen anytime soon, or have anything to do with Android L. Presumably, the changes might not require Android L, and could be done mostly through app updates and Google Play services.