I don't know about that, but I'll tell you this: "more and more cars" with HD installed at the factory, despite the giddy glad tidings of the six HD fans who post here, is NOT a good thing. Let me explain why.
We all know that - while there are anecdotal reports of HD working "JUST FINE!!" in certain markets with optimal terrain, few adjacents and high power - the best that can be said of HD Radio performance is "unpredictable and often unsatisfactory." Consider the typical consumer. While, as informed professionals, we might expend the energy to troubleshoot the inevitable reception problems, muting and mode-hopping, for each one of of us ten civilians out there will simply assume "radio reception sucks" and turn to mp3s and satellite.
The foregoing, of course, applies only to FM HD. The AM is useless.
It's another instance of "be very careful what you wish for." We can only hope that the industry will have some success in instructing listeners how to defeat the digital when it causes erratic performance.