"Make all car windshields out of photochromic glass that darkens to a moderate sunglass tint when exposed to sunlight. This innovation would improve driver comfort and safety, especially when traveling into the blinding glare of a rising or setting sun."
Well, first of all, I should mention that 'product extension' can be considered as a part of a product life cycle. The main aim of the product extension strategy is to make a product to stay in the market for a longer period of time, to make more profit and don't let the sales revenue start decreasing.
I don't think that this is an example of a product extension stategy. It's about cars as a whole technlogy, there is no brands mentioned. I think it is just a development of technology that will make cars better. Cars will be used until a new way of transportation will be found, therefore cars as a techology don't need product extension strategy.
If it was about a particular car, we would be able to call it product extension strategy.