We don't need a new GPL.. ML creating a derivative work is still a derivative work. So if said derivative work ends up in a non gpl compatible code base, that code base is then violating the license. I would assume that GitHub/Microsoft would have had the forethought for this, but who knows. And in any case, I am not a lawyer...
That is what is supposed to happen. However, reality is different. Copilot keeps being shown to simply regurgitate whole code snippets without modification (and more importantly without attribution).
I worry that violates freedom 0, although maybe you could add something about the "use" applying to humans. But then what about bots and scripts running automatically?