Re: Too late!
"I cannot think of a single thing I have which relies on time values and is over ten years old, let alone twenty, but that's just me."
OK, a specific, concrete, example of something large and heavy that goes fast and that depends on an embedded system...
The minicomputers in some diesel electric trains date from 1980s. These won't be Linux kernel based obviously, but a diesel electric train tends to have a long life...
Perhaps the ones being built now do have Linux based controllers. Perhaps these are 64 bit. Perhaps if 32bit, then they will simply stop working (safely) on the relevant date and display an error code. Transport is, fortunately, conservatively managed and suppliers will take a careful change management approach to maintenance. Problems should surface in advance.
The wider point: embedded systems are gleefully being added to many industrial and transport systems to reduce costs, improve monitoring, and provide hard data on use. This is an *expanding* market. Some suppliers will go bankrupt. It is possible that entire business models will be discarded, but will leave a layer of technology in racks in basements ticking away (e.g. DC mains power for 19th and early 20th century lifts/elevators in some cities - now mostly provided by local rectifier/choke sets).
Timely and repeated restatement of this issue and the mitigations available will help to offset any disruption and is best started *now* as most of the systems that will be functioning on the date in question have yet to be designed/implemented.