To me, the 'witch hunt' refers to finding evidence of collusion with Russia by Trump.
Trump and his supporters are still using the term because no evidence has yet to be made public that Mueller has found 'Collusion with Russia by Trump.' The term witch hunt is used by people that want to say there is no evidence of wrong doing associated with whatever the subject matter is, because a witch cannot be found because they don't exist, and so they are implying that no evidence of wrong doing can be found either, because like a witch, it doesn't exist.
However, at this point, even though there has been no evidence made public of Trump's collusion with Russia, Mueller has not made his report public and his investigation doesn't appear to be concluded yet. We'll know when he reports to Congress.
None of the guilty pleas or convictions so far have anything to do with Trump colluding with Russia to influence the 2016 Presidential election.
So the thread title takes two completely unrelated situations and inaccurately conflates them as if they are.
All that said, if the Mueller probe stops without any evidence of Trump colluding with Russia to influence the 2016 Presidential election, either ending early or ending upon completion of the investigation by Mueller, the current convictions and guilty pleas stand.