To keep subscribers year-round for CBS-AA, it's doubtful they would drop DSC if season 3 goes well all around. These shows can co-exist and compliment one another in wonderful ways. I would expect PIC to do awesome numbers, but that doesn't mean doom for DSC, since they're not in competition with one another.
Of course you're right. But you know there will immediately be people who will want to make it a PIC vs DSC debate every step of the way.