Well Msl I do think you are jousting at windmills. All the dire predictions could happen; many bad things could happen but we cannot be on guard against every possibility without losing our sanity. We have to attempt a reason appraisal of odds we are comfortable with and go with it. The amount of years and the nature of the killing mechanism with these acids with no sign of resistance (in any well credited test) makes that possibility very remote. I am comfortable with that assessment.
There is a possibility; some say a certainty that the tropilaeleps mite(sp.?) is on its way. That is probably a much stronger possibility than the risk of varroa becoming resistant to the physical damage of these organic acids. Much of what humans are doing today is very unwise. The problem we are facing to day is an example of removing geographic isolation of pestilence.
Like I said, I think there are greater dragons to slay.