The Constitution will never again be amended, because you will never get 2/3 of States to ever agree on anything, ever.

As it stands, such an amendment would require rural citizens to effectively eliminate themselves from the electoral system. They will never consent to this and why would they? Since State legislatures are also not pure popular-votes, this assures that nothing remotely resembling this will ever happen. No rural voting district will consent to being washed out by a large metro.