We end how? The only grounds for impeachment are not being in "good behavior". We had a Senate that couldn't impeach a President for committing a felony in office. We have a Senate who didn't have the spine to deny Arlen Specter the Judiciary chairmanship. Do you think there would be any hope of removing Roberts because he "pulls a Souter"? This is why the NOMINATION process is important. Once confirmed he's in regardless of whether he turns out to be a closet activist. Done deal, at least in this universe.
If we don't get a majority of real, originalists on the SCOTUS immediately we end as a nation.
Like you said, we couldn't impeach the traitor, we couldn't prevent the backstabber from chairing the judiciary committee,
we can't/actually won't secure the nation.
If Roberts is a Souter clone the nation is finished.
It won't take but a few more years until there's nothing left.