This is apart from MapMaker, and their dev teams, and their software improvements.
For instance, if you look at directions in India now, they're awesome, since they tell you landmarks to look for on the way [pass by * on left], at the intersections, etc. http://goo.gl/maps/b8w15 for instance.
My guess is 95% will take 3-4 years - once they accept they have a problem.