Your subject line and and the headline you quoted from Cointelegraph.com is misleading because it is not entirely true.  

Coinbase's CEO stated the following, “A committee of internal experts is responsible for determining whether and when new assets will be added to the platform in accordance with our framework. These individuals — and all employees at Coinbase — are subject to confidentiality and trading restrictions.  As of the date of this statement, we have made no decision to add additional assets to either GDAX or Coinbase. Any statement to the contrary is untrue and not authorized by the company.”

Coinbase's president stated the following at the end of 2017, "So we have published a digital asset framework which outlines the criteria we look at for any particular asset before we list it…You need to pass those exams before we would ever list the asset…suffice to say that we have a framework out there and we have a lot of people campaigning for new assets."

So, it seems that Coinbase is looking at additional currencies for inclusion on their exchange, however, they have not iminent plans to do so.  That does not mean that they won't decide to add one next week, whether it would be XRP or some other currency.