It's never a good idea to store large amount of coins on exchange, but sometime you just can't avoid it. Leaving just a little amount of bitcoin on the exchange won't hurt, as long as you can afford the lost (if happens). Sooner or later exchanges will give you the forked coins, it's just the matter of time (XAPO has offered BCH in early October, the fork happened in August...)

Right now most of them are saying that they don't support it and won't list it. I expect it to be listed on bittrex, maybe polo as well, yobit maybe.
Before the last fork people were saying that we shouldn't keep money on exchange, that it's unsafe, but it all went smooth. Just remember you can keep BTC in your wallet and redeem your coins after the fork with no risk involved.

During the last btc fork, my friends put their bitcoins on bittrex exchanger and they told me they received their new forked bitcoins. But you have to make sure before you put them there. Follow the official updates.