10Base-T1 might be a real thing someday. You might just want RS-485.
Being able to obliterate USB, CAN, and RS-232 (to a lesser degree--RS-232 is really reliable but the problem is generally in frequency drift if you don't have a crystal anywhere) in all of my designs and replacing it with ethernet will dramatically improve the reliability of my hardware. The only places I don't currently have ethernet in my designs are where I'm limited to a single pair of wires.
As for RS485, it doesn't really offer me anything that I don't already get with CAN.
However, everything has to work, reliably, in less than ideal environments--mostly high-voltage spikes caused by differences in ground potentials.
USB is a PITA because while data is differential, connection detection is not. So, spikes cause USB disconnects and drivers never cope with that.
CAN is a PITA because it is limited to 8-bytes per message. Good for transducers and 8 bit microcontrollers--not so good for complex control and 32-bit microcontrollers.
Ethernet hits a really great sweet spot of fully-differential and nice single packet size for a 32-bit microcontroller--program like it's 1989, baby.
IEEE had a working group on this but I hadn't seen any actually shipping chips that mortals could get their hands on.
(Edit: Apparently still vapor. Still can't find a source for the Marvell 88Q1010 & 88Q2112.)
(Edit: Only thing available seems to be this which is almost certainly some gigantic FPGA solution ... https://beyondstandards.ieee.org/connected-vehicles/intrepid...)