6-8" are mostly used.
As for the growth in sales, it's a bull sh*t! They sale certain products. And they tell us we will buy more. What for? What if we won't buy them? I think that this article is nothing more than a marketing technology.
Any thoughts on whether the norm will be touch screens? Once the screen is in the car the car maker might as well have the screen used for other things like audio and temperature control. It would seem that the best way to manage such controls is with a touch screen. However it could be that the car makers will just put in the screens to satisfy the law and not add anything else that will cost them any money even though once the screen is there the cost to add the controls is much lower.