Meanwhile, another question, what would happen if, lets say a token is rather a junk token, abandoned by dev, stuck only on one exchange, with only sell order with no buy orders. In short, take a look at wavesdex, they have plenty of weird tokens. Let's say someone wanted to swap token with these characteristics to btc or eth, what will happen then? Does the swap even possible?
A junk token is a totally normal token from the point of view of its smart contract. This means that such a token, if its smart contract is not killed (and it must be provided for in the smart contract), it will continue to exist as long as the Ethereum blockchain.
So, on an exchange, if there is a sell order for such a token, and you place a corresponding buy order, then the exchange will be done, and you will be the happy owner of such a token.
Alain Saffray