My definition of Ethernet is a cabled infrastructure, using the Ethernet frame format, which directs frames to end systems via a non-hierarchical address structure. So this limits the practical size of a single Ethernet "concatenated network," because frame addressing has to be to each individual other host in the network, multicast or broadcast.
In other words, it's a "layer 2" network technology. It's longevity, IMO, is largely thanks to sticking with layer 2, and not attempting to become a global network (as ATM did). So for instance, normally Ethernet depends on the IP layer above it, to make it useful. Ethernet DOES NOT attempt to compete with IP. As a result, any number of changes to IP, including the big one from IPv4 to IPv6, have no effect on Ethernet. Ethernet improvements can continue independent on what rides over Ethernet.
Depending how you define "real time," Ethernet is already doing many jobs, e.g. on the factory floor, that were previously considered "real time control."
The sheer volume of Ethernet in automobiles - either for data or power delivery makes it very exciting. THey are simply problems that need to be overcome and you know i have tons of faith in 802.3's ability to solve these problems. I get really excited when i start to just let my mind wander and think how people will want to take advantage of a network in their car.