Merit criteria for promotions in Indian Foreign Service also ?

It is very clear that the next five years of Modi Government would be golden years for Indian Foreign Service officers as the PMO may choose the best talent for key foreign missions from even very junior batches. Like the defence services, merit is likely to be the biggest criteria for promotions even in the Indian Foreign Service after a level soon as indications are coming in. What does it mean? A senior officer gets superceded for top job ?