Coinbase will support the Bitcoin Cash fork called Bitcoin SV. That said, Coinbase tends to take their time in releasing forked assets and allowing the trading of forked assets.
Further, if one of the two chains doesn’t meet Coinbase standards, there is a chance they will never support it (Coinbase never ended up crediting users for the Bitcoin Gold fork for example).
Those who want immediate and ensured access will need to choose between being in control of their private keys and other exchanges (a good choice is Poloniex, as they are already trading IOUs of both chains).
In sum, both third party exchanges and wallets who support the fork and being in control of your private keys are valid choices, but it is likely (based on history) that Coinbase will take its time offering the forked asset for trade or withdrawal in the case that they do consider the chain viable. Do your own research here folks!
Learn more about the Bitcoin Cash fork.