Conquest to remain in 2016 season
It seems, Blizzard decided to keep the match format, which was used in the last World Championship. Not all the players and tournament organizers agree with such decision though.
Conquest was the match format of the second HearthStone World Championship. Briefly, the format implies best of five matches with only 3 decks, chosen by a player before the match. A player can't use a deck in a match after he or she won a game with that deck. The loser of the game is free to keep his deck for the next game or to change it. This means that to win a match a player must win with every deck he picked for the match. Players know the classes, which their rivals picked for the match, but they can't predict particular class for a particular game.
On the whole Blizzard was satisfied with the format, having characterized it as "very successful". However, not everyone shared the opinion of the game developer. Many professional players stated that they're not satisfied with Conquest, claiming it prevents the experiments with the decks and "freezes" meta. Furthermore, the organizers of some tournaments, supported by Blizzard, decided not to support the format. For example, the upcoming DreamHack Winter will use last hero standing format, which implies that the loser changes deck, not the winner.