Why would used cars drop in price? Since no one is buying new cars there's no supply of used cars. Lower supply means increased prices but demand is probably down as well so almost no change.
Leases come due. Cars hit the used market. You also have rental companies dumping cars onto the market since business has collapsed. Hertz might be going into bankruptcy. Repo's are another thing to consider along with private sales when people can't afford them or need to raise money.
There is a big supply of used cars coming. Rental agencies are offloading cars because they have storage issues with nobody renting their vehicles. However, lots of the car auctions are closed so that could prevent the prices from coming down.
They're actually about to reduce used vehicle supply to artificially inflate market conditions above where they're going to sink to. The corporate gangsters in Detroit are working on Cash For Clunkers part 2 (which will harm the poorest vehicle buyers the most over the span of years as supply is reduced, just as it did last time).
When I bought my current used car, in cash, the dealer offered it on financing for 0% or 0.9% or something very low — no impact on the selling price. It wouldn't have been a terrible decision to take the super low interest loan and put the purchase money into my investment portfolio instead (just another form of leverage). I paid cash anyway, because I went in intending to, but characterizing all financing as extremely desperate is misguided.