No, I have never heard of the term WorldCupBracket before in relation to the greatest tournament on Earth.
WorldCupPlayoff is not really much use, at the moment as the play offs have already happened and it was to see which team that finished second in Euro groups as well as 1st place in Oceania and the 4th place (I think) South American teams qualified for the World Cup.
Also, as has been stated, the winners are nearly always refered to as World Cup Champions and not World Cup Champion
PM me if you need any more info on the World Cup