I don't see ripple being one, you have to own twenty just to have a wallet and the value right now is too low compared to the cost per ripple and the fees on Coinbase. I could definitely see BCH or DASH maybe even both being added, valuation of the coin versus fee cost makes sense for coinbase from a business standpoint especially with volume included. Possibly XMR, hadn't thought about the privacy and KYC rules on that one until you pointed it out. Until I considered that it was my strongest contender for being added and still is in my top 3 guesses for what will be added. Great video and steemit post.