I don't think that BA have flown it for a while. Almost certainly dropped because it was loosing money. It was likely a low yield route. (How many multi-nationals have large offices in Dhaka?) Resources could be shifted to a more profitable route. It will be restarted when an economic appraisal suggests that it will be profitable.
Don't hold your breath. BA still doesn't fly to Seoul or Taipei which it dropped a number of years ago and I would have thought promising routes. Mind you in those cases it is up against high quality opposition and would have to offer non stop service to be competitive.