I dont think that the secondary market will be effected from this. If anything it may even do alot better. Sadly, because there are no cons and comic book shops are closed/ing theres basically only one main outlet for books - online. And I think that will only get stronger and stronger as time goes by if nothing else changes. I've had the strongest month in sales in March, and not alot of it were keys/big books... TONS of $5-20 i never dreamed Ill ever sell.
As far as new books, who knows, maybe Diamond will never open again, but there are so many ways to change the status quo positively.
The big 2 (3?) may chose to implement conservative subscription services once again. the indies may go the kickstarter route. Or maybe they will both combine and create a new online distribution channel.
Brick and mortar will now focus on selling online, so even though they are closed now, they still have inventory to move and if focusing on just that, at least they will be able to sustain operation while this play out.
None of this is easy, but one thing is for sure, the industry will not die, the market will sustain, and maybe a new generation of distribution will be born
lets wait and see