There is no reason to assume that TCP/IP or QoS will be standardized upon or even used at all here.
There is every reason to assume that. The car manufacturers are working hard not just to standardize on IPv6 in general, but in fact to have a common approach to such things as address allocation. QoS will be much easier to handle with ethernet, not because it is less complex but because the code is already written and widely deployed.
Also, QoS is a total dog if you are trying to employ it on consumer grade equipment.
I must admit that I have never tried to use QoS on ethernet with consumer grade equipment. Why would you want to though? Generally you have precisely one switch at home, and that switch is typically capable of simultaneous full speed on all ports, so it only drops packets if multiple input ports are trying to send more than 1 gigabit in total to one output port. I have difficult imagining that scenario in a home.
QoS on the WAN is entirely different, but the WAN is typically not yet ethernet, or at least not ethernet at standard speeds.
Perhaps FIOS is still atypical. 300Mbps/75Mbps is what I've got. Pity I can't get 300/300.