We usually solve the tragedy of the commons situations by adding a regulating authority. One could argue that that's one of the main reasons for having governments. Of course we don't have a world government to appeal to here and the number of nations with launch capabilities is rapidly growing. But as private organizations lose profit from worsening Kessler Syndrome they will push for a solution, since this a everyone-looses situation, not winner-takes-all. I would predict we wind up with another UN organization, similar to the ITU.