Current:
I haven't noticed much change in asking prices due to Covid, there was already some "softening" through 2019, but the effect of Covid on people's economies may still take us into this winter to really show itself.
Using home sales as an indicator, the economy is doing well, and interest rates, even on used cars, are low. A friend got a 3.9% rate on his used Ferrari. I think a good number of people didn't spend and banked money by isolating and not traveling as much this spring and summer. Stock market is still doing well. Buyers might be waiting though, it would be cool to find out if muscle cars are on the market for longer before selling - to measure the demand.

Near-term:
Nobody has a crystal ball, but my guess is by spring 2021 you will see average muscle car prices dropping more noticeably. The trickle down effect of the trillion dollar stimulus packages will be wearing off, rent relief and stimulus loans will be due.
The expanded money supply will drive some inflation, meaning prices on everything will be up (propping up some muscle car prices), and those in worse economic shape will be selling non-essentials.
The only offset we all hope for is that all the jobs come back, but I wonder if job supply won't stabilize before there is a significant dip in consumer (muscle car) spending.

Long term, its the same dynamic as always -
Owners grow older and older, and eventually sell their [insert any era] classic car, so more cars are on the market, and fewer people are around that are interested in buying them.

The only question is how long it will take, probably 10-15 years until only the "halo" cars retain their value.

Cheers,
- Art