Polo is late. I believe BCH will dump.
Still better that Coinbase, which will keep it stuck until January 2018
"We are planning to have support for bitcoin cash by January 1, 2018, assuming no additional risks emerge during that time."who knows, maybe it will be a big surprise.
At least they have changed their mind to support bch, even in Jan 2018.
There is no mention that coincase will allow buying or trading of BCH
Once supported, customers will be able to withdraw bitcoin cash. Well make a determination at a later date about adding trading support.
This decision is down to the brewing class action lawsuit I suspect coinbase still does not support this and you may just find the only option is to withdraw your BCH balance to another address.