Usually, the coin price will drop quickly after fork. That being said, you will loose a lot of money compare with keeping coins at a third party exchange. Because the bitcoins in an exchange can safely claim bitcoin2x very soon and it is able to trade within a few hours after fork, even if the reply protection is not ready.
I recommend you guys keep bitcoins at an exchange in order to have an earlier bitcoin2x claim, and sell earlier than who keeps coins at a wallet.
Having coins stored on an exchange because they make it easier for you to split coins(EG, that you don't have to do it yourself for the splitting process) is very dangerous.
Trusting exchanges with your hard earned cryptocurrency is a mistake.
BTC-E had issues where the govt raided it and took a bunch o fpeople's crypto. MTGOX lost a ton of bitcoins, like 800,000... Other exchanges like Bitfinex get hacked. I think coinbase was hacked too at one point.
Don't keep it at an exchange. Keep it in a wallet you control the private keys to and you can split the coins yourself later when a guide comes out.