It's already happening. Auction houses are down significantly, and you're seeing like 70-80% of MMR value at auctions for vehicles (
https://publish.manheim.com/en/services/valuation).
It depends in which manner they need to liquidate, if they can hold the inventory it often makes sense to do so instead of losing the 20-30% of market value liquidating it (you just do the calc of depreciation per day versus selling right now).
You can't really liquidate new cars, because there's regulations around selling new cars that prevents folks like Vroom, Carvana, Shift from taking on that inventory but those are the only folks who could really afford to do so with their respective funding from external sources.
Financing incentives are risky, but you account for that with increased income verification and other items - the deferral of payments for 90-180 days is getting more and more common.
This situation seems different from the 08 recession, as lots of folks _should_ get their job back once things are opened & we get back to a new normal so if you treat the risk as such you're hoping that 90-180 days is enough of a time period to have people be able to afford the loan they've gotten.
The real looming issue is you have ~4M or so vehicles coming off-lease later this year, so you will have an incredible influx of used vehicles to an already saturated market leading to great deals for consumers but not ideal times for most folks.
The harder part of selling online for dealers is that their money maker is in the hard-selling of ancillaries (Warranties, the "paint protector" and so forth) plus the F&I office (financing and insurance) but if you can't hard sell customers anymore then the majority of your profit center is gone so it's having a material impact on the dealers.
Happy to expand more or answer further questions as I work in the auto space.