The Senate rule changes must be debated, hence, any rule change can be held up by a filibuster. However, the majority leader has the option to strike a rule with a simple majority vote.
I think you end up with circular logic on that, since the option to strike should be governed by the rules, hence, possible to filibuster as well, but that sounds like a Supreme Court Consitutional Crisis if you ask me.
Now, if one party, or a sub-division of multiple parties, colluded to get the 67 votes, they could pass anything they wanted into the rules to block all legislation but their own. Doubt they would be in office for longer than 1 term, or if they even finished the term, but that's the way it works.