Winning your own game is obviously a good way to achieve that, but it may not be necessary and it might not be sufficient either. If every other Yellow player dies on Turn 10, you don't even need to finish the game! And if every other Yellow player wins their game, you have to do more than just win - you have to Win Big!
So there's no point in bowing out before your time is fully up - how long you live is part of how well you do. And only the final standings at the end of the match will count. It doesn't matter if you led the game for 17 turns if everyone allies against you and knocks you out on Turn 20!
So be careful how you play, because the objective of the tournament games is very different from the simple win/lose objective of a single normal PBEM game!
Finally, there will be a "Head-to-Head Warlords Ladder" which will start after the 1st round of the tournament and run continuously thereafter, and players will be seeded on the ladder based on their success in the first round, so even if you don't do well you should stay in the tournament and try your best so you can get a good spot high up on the ladder!
(From most to least stupid. Names abbreviated to protect sore egos.)