If Bitcoin price pumps from $1300 to $3000 in few hours, nobody would make profit from it, because the exchanges wouldn't allow you to sell your Bitcoins and make the fast profit, it would bring a big loss for exchange sites.
Do you agree with this?
I didn't know what will happen, but I think it can be a possibility. I think they will be waiting for hours or maybe days before they can allow someone to sell it. But, if you can't sell it, maybe you can convert it. I am using a coins.ph wallet where we can convert bitcoin into fiat in a second, so I think if they did not allow me to do a cash out, I will be converting that bitcoin into fiat. And after a dump, I will be converting it again to bitcoin.
An exchange that did that will probably go bankrupt since no one will trust them again, it is one thing if that was related to technical problems on their site, but if they forbid withdrawals or the ability to buy and sell bitcoin then that exchange is surely going to be mistrusted for a very long time if not forever and since trust is very important in bitcoin, the future of that exchange is going to be at jeopardy.