First of all, what is Coinbase's custody? Take a look at yourself – https://custody.coinbase.com/
According to the website, Coinbase Custody is:
"Custody through a regulated and institutional broker-dealer. collaboration with ETC, SEC-registered broker-dealer and FINRA member, Coinbase Custody is proud to offer a service that combines the safety excellence of Coinbase's cryptographic resources with the broker-dealer financial reporting experience. "
The essence of this is Coinbase Custody pairs a cryptocurrency exchange platform (Coinbase) to ETC, a platform for trading securities and other tokens. So how it is, Bitcoin, Bitcoin Cash, Ethereum, Litecoin and Ethereum Classic are all available through Coinbase Custody, with XRP, Monero and Dash that are supposed to be added later, along with an ad that also suggests that Coinbase will add all token ERC-20 to
According to Coinbase:
"We are pleased to announce our intention to support the Ethereum ERC20 technical standard for Coinbase in the coming months, paving the way for ERC20 resources for Coinbase products in future, even if we are not announcing support for specific activities or features at this time, we are announcing this both internally and to the public in a manner consistent with our process for adding new resources. "
View more for yourself, here .
So, what's going on here?
It appears that Coinbase is trying to allow the storage of XRP, Monero and Dash through the Coinbase custody platform.
This would allow the storage of resources such as XRPs within the Coinbase platform. Obviously, this does not mean that XRP will be published on Coinbase, but this new move allows Coinbase to exist within a Coinbase network, even if it continues to be considered a security by the community, even if a decision on this  According to Sam McIngvale, Coinbase Custody Product Lead:
"Coinbase Custody is exploring the addition of many existing and future cryptographic resources for storage, and will work to add them as quickly and securely as possible. We have not yet considered these assets for trading, we are making this announcement internally to Coinbase and to the public at the same time to remain transparent with our customers on support for future resources. "
See more for yourself,  here .
The most important thing though:
"These goods are taken into consideration by the Custody only at this time and this announcement has no influence on products based on trade."