Take any rumors of coins being added to GDAX/Coinbase with a grain of salt!
I see different people saying what the next coin to be added to Coinbase/GDAX will be. First it was Ripple, then ADA, tomorrow it might be DOGE. Who knows? It's at the whim of the shiller/predictor to determine which the next coin will be. Speculation is great, but don't let it drive your decisions with money. Unsubstantiated claims should never be taken as anything more than food for thought.
https://twitter.com/brian_armstrong/status/948996330952654848