Note that Bitstamp, another large exchange, took a similar stance as Coinbase and has issued an update stating customers will receive their BHC balance:
For those of our customers who chose to leave their BTC on our platform at the time of the fork, we recorded their BCH balances for the timestamp of the last common block (block 478558), which is 1 August 2017, 13:16:14 UTC.
These BCH balances will be made available to our customers as soon as it is safe to do so. If and when the Bitcoin Cash system has been thoroughly tested and is sufficiently stable, we will then consider listing BCH. However, a series of technical, safety and regulatory requirements need to be met in order for this to occur, and it is still too early in the day to make realistic predictions about the timeframes involved.
https://www.bitstamp.net/article/bitcoin-cash-our-position/
For those of our customers who chose to leave their BTC on our platform at the time of the fork, we recorded their BCH balances for the timestamp of the last common block (block 478558), which is 1 August 2017, 13:16:14 UTC.
These BCH balances will be made available to our customers as soon as it is safe to do so. If and when the Bitcoin Cash system has been thoroughly tested and is sufficiently stable, we will then consider listing BCH. However, a series of technical, safety and regulatory requirements need to be met in order for this to occur, and it is still too early in the day to make realistic predictions about the timeframes involved.