Don't be shocked if Coinbase adds Ripple next. If that doesn't show their true colors, I don't know what will.
I presume Coinbase's ultimate aim is to be bought out by Goldman Sachs et al. They are not anyone's friend and don't have anything's best interest at heart other than their own value.
No one should be shocked by this, but I am slightly surprised at the blatantness of this particular move taking place during blockchain spamming, difficulty readjustment, all time high in attention and super high fees.