A slightly different/simpler approach is just to wait for the Page.OnAppearing event to fire. This event ensures the Xamarin.Forms renderers are correctly hooked up to the native underlying view. Generally I'd recommend to wait with doing too much to the MapView until this event fires.
Currently LocationDisplay isn't settable, which prevents us from linking it to the native view until that link has been established (we're hoping to make it settable so this specific change in behavior could go away). It was, believe it or not, a bug that there was an underlying native view prior to the appearing event, which caused a slew of life-cycle issues. that we now addressed in Update 6. Unfortunately you might see a couple of these behavioral changes due to us fixing this problem.
Good feedback that we should have documented this change in behavior. We'll try and get that addressed.