Remove of airdropped merits will make old Senior Members, Hero Members and Legendary members feel paranoid, like what theymos said on misuse or too serious use of trust system months ago. Good old users can rank up again, even their airdropped merits removed and they will be deranked. They definitely don't have issue to move up again, just need a little bit time. Nevertheless, once again, I don't think airdropped merits will be removed because of probably paraniods.
I think it's pretty unrealistic to expect that airdropped merits may be removed in the future, but this is up to admin to decide. Still, I understand some members who think differently on this, but old ranking up system is just upgraded with merits, and anyone who is ranked without merits is invest lot of time to reach Hero or Legendary rank.
Maybe airdropped merits could be assigned in a slightly different way, so that every member who hold any rank should prove itself by earning some extra merit.
For example every Legendary member could only get 900 merits and become Hero member, and every Hero member 400 merits. Maybe this is not best idea, but it is much better then take all airdropped merits.