This is a non-issue because no one actually expected to make a car like Google's prototypes. Google isn't even trying to get into the automobile business with this technology. That's not what they do. They sell tech and software services. They're just trying to show their prospective customers what their tech is truly capable of. The real automakers like GM, Ford, Toyota, etc will use Google's tech in the cars they produce and I don't think anyone ever expected them to make a car without a steering wheel. I'm sure they'll eventually include "automated driving assist" as an option in some of their vehicles but they're still going to sell cars drivable by humans.
Don't get me wrong, it did need to be clarified in the laws...but no one was actually planning to build a real car without pedals and a steering wheel.