Coinbase is adding Dai (DAI), Golem (GNT), Maker (MKR), and Zilliqa (ZIL). With that said, only some coins are being added for US users.
Here is the breakdown direct from Coinbase:
“Support for GNT and DAI will initially be available for Coinbase Pro users in the US (excluding NY), the UK, EU, Canada, Singapore and Australia. MKR and ZIL will not be available to customers in the US, but will be tradable in the UK, EU, Canada, Singapore and Australia on Coinbase Pro.”
The connecting thread here is these are all ERC-20s (Ethereum-based tokens). It seems that Coinbase is getting comfortable adding Ethereum-based assets that meet their criteria. They have already suggested many more listing to come.