Generally, they won't, although it's possible that some cats might be bitten to death. There are many reasons why cats fight, such as territorial disputes, excessive force during play, being in heat, or jealousy of their owner's favoritism. If the cats only suffer minor scratches during a fight, there's unlikely to be any serious problems, and they won't die.
Regardless of the reason why cats fight, as the owner, you should stop them in time. If there are wounds, you should treat them promptly to prevent infection, inflammation, ulceration, or even suppuration, which could lead to death. Therefore, you should pay close attention to your cat's condition regularly.
