With all the mention of connected experiences, it would be a crime to split destiny into fragments with PS3, PS4, Xbox 360, Xbox Next, PC. They need a giant persistent world, only way to do it is cross platform. It's a must for this type of game. Destiny should be about 1 universe, not 5.
Only major problem I sense, which probably has been for all this time, is the PC players and their mouse/keyboard setup. Coop is fine, but during competitive gameplay, PC gamers will have the edge and uneven the battleground. But then again, the players will be mix and matched between console and PC so I don't see much problem.