A promoted henchmen is no longer a henchmen; he is now 100% a hero. Thus, according to the wording, "roll a D6 for each henchman who is either an orc or a goblin," your promoted orc would not suffer animosity.
As a quick aside, note the part of the animosity rules which states, "if the nearest friendly model is an Orc Hero, the warrior behaves as if a 2-5 had been rolled on this chart." Most people new to the warband miss that bit.