For any major event such as the World Cup, you shouldn't assume that prices will come down. Particularly since Sochi isn't particularly well served by international airlines, so there is little competitive pressure. TK can almost name their price, since they will be the best option for football fans wanting to fly in/out of Sochi.

Perhaps after the World Cup draw you might have a better picture of the situation, depending on who is drawn to play in Sochi around your travel date.