Fifa World Cup Brazil 2014 was released before FIFA 15 and had no effect on its sales at all. Not at launch, nor regarding legs.I mentioned upthread that the World Cup titles didn't show up either; FIFA 15 appeared in the same year as World Cup 2014, so it might perhaps be that people weren't in the market for two separate FIFA titles that year, splitting the userbase?
Fifa 15 is still the third biggest Fifa launch in the UK (at retail)