Where are the 67 votes for the amendment? The only thing that's missing in going from amendment to impeachment is the belief that impeachment is an acceptable option. And that depends largely upon the people who are in the forefront of the push for the amendment.
There is a difference between democrats voting for an Amendment and voting to impeach judges for cause. One's not gonna happen, the other, if DOMA, is any indication just might.
There are other methods to be employed by Congress if they so choose. They have article 3 powers to simply tell SCOTUS to keep their hands off certain issues. That would be doable, impeachment is not going to happen, the politics are too thorny.