I traded in both my original Xbox One and PS4 when I upgraded to the PS4 Pro and One X. I don't do that typically, but I just didn't see the point in having them. It was really easy to get rid of that original Xbox One, let me tell you.
Until plans are backwards compatibility/cross generation support are made clear, I'm planning on hanging on to both half step consoles for now. I don't see myself trading in either of them. I didn't trade in my original PlayStation or PlayStation 2 because of the backwards compatibility in the launch PS2 or PS3 respectfully.