With out "ideological slippage," libertarianism cannot exist. Its built in to the philosophy. Of course the monarchists will want a politburo to ensure that the natural outcome is not tampered with by any revisionist or outside influences. But this is all academic, as libertarians will have long settled the problem prior to gaining popularity enough to effect any significant societal changes in their direction.
Well, that was the point of my irony. I agree with you that libertarianism (whatever that really is) will naturally evolve into a "rightwing, highly conservative monarchy", unless some comissariat prevents it.