Doing a little poking around i stumbled across this bit of information. I am not sure how long this has been up and maybe i am late to the game but it sure is interesting.
Supported Coins
Directly from Coinbase.com : https://support.coinbase.com/customer/portal/articles/2630943
From this chart it looks like Ethereum classic and bitcoin cash and bitcoin 2x are already supported on coinbase and Gdax. Not only this but if you type ripple into coinbase support search bar the supported coins link will pop up..... hmmmm
Makes you wonder....
It makes me think Ripple has a really good chance of being added if not chosen already....
What do you guys think ??
This also happens when you search Neo, Eos and several other tokens, it's probably just a curated list to redirect people to their list of supported tokens.