Exchanges don't care about the price. There are many coins that trade with some volume at right around a satoshi (0.00000001 btc/coin).
If volume drops to very low levels, however, some exchanges would consider de-listing.
Steem and Steem Dollars have a long way to go before that happens.
Even if exchanges delist a coin, I'd expect a community to survive for sometime.
Thank you for the reply.