The only issue I see with this idea is that a lot of people tend to stay with the CarPC because of screen size. I can't imagine rolling down the road trying to simply glance at my iPhone for all that info. It can be done to be sure but, it's much easier with a 7 inch screen than a 4 inch screen. The devices you are referring to sound a lot like MIDs or UMPCs and unfortunately, they seem to be heading out the door.
I use a UMPC as my Carputer and believe me I love it. It serves as a 7 inch touchscreen carputer when I need it to yet, I can take it with me when I leave and use it at home or work and I do. I have a mount in my car and just pop it in place and connect the USB cable which runs to my glove box holding all the peripherals. For me, it's the perfect solution. But even among carpc enthusiasts, I'm a minority.
Realising the opportunity to reach the CarPC market, a lot of the UMPC manufacturers are even making car mounts with built in GPS antennae to make themselves more marketable but, again, the market seems to be slipping away from them.
The mobile computing market seems to be going the way of the iPhone and the MID but, I don't think the face of Carputing will change with it. But hey, that's one guy's opinion and I've been wrong a lot.