This could be great for people like me. I won't buy a car that's too new because I don't want a "connected car". But if the cell deprecation means that there's a bunch of cars that are physically unable to connect, and are less desirable to most people because of that, I may be able to get a newer car, cheaper, than I was expecting.

5G and LTE were developed with the idea of spectrum sharing. (LTE was intending to share the spectrum for multicast TV, but either way, it's a way to let other things talk in the same spectrum) If the control channel runs in a 4G compatible mode, both 4G and 5G devices can attach and individual timeslots (or whatever the correct term is, cause it's not TDMA) will be encoded differently. Maybe it's a little less spectrum efficient on the control channel, but it makes it more likely to keep 4g devices online than in past updates where a whole block had to be 2g, 3g, or 4g.

Hopefully car makers learned from the 2g/3g shutdown to at least have a way for the (eventually) obsolete modems to not drain your battery when there's nothing to talk to. But then, my 2013 ford shipped with a 2g modem, replaced under recall with a 3g modem, and last I checked doesn't have a viable 4g modem (connected features weren't very useful anyway).