I will likely never consider a GM so if they want to further implode sales let them. For them to say they will produce a better product, this is not likely. Would you want the first year beta software or the multi-year, proven product. Why do car makers think they are good at software development? Just look at the horrible infotainment systems across so many brands. The best approach is to partner with proven leaders.
Also, there are so many apps that support carplay. Many of them local to specific markets, like payment for parking, local radios, apps for charging, a gazillion audio apps (various podcast apps, music streaming, audio books) etc etc.
The selection on GM will be severely limited, and they'll stop updating it pretty soon too - compared to just buying a new phone to connect to the car.
This is bad for car buyers, and GM's dreams of nickling and diming car owners and application developers alike will just end with lower sales and unhappy customers.
