While Warner Brothers might have dealt a knockout blow to the format war, it's possible that Fox might have thrown a set-up jab.
A story from the Wall Street Journal states that Fox's firm stance on the Blu-Ray high-definition format sealed the deal for Warner to go Blu-Ray exclusive as well. Here's what the story said on that matter:
"Toshiba was still working hard last week to court Warner and News Corp.'s Twentieth Century Fox to use HD DVD exclusively. Warner was considering it, people familiar with the matter say, but when it realized Fox wouldn't leave Blu-ray, decided to go with Blu-ray exclusively as well, to bring an end to the format war."
The article went on to say that Blu-Ray still had some obstacles to overcome.
"Even with major studios on board, Sony must still win over consumers to Blu-ray. Consumers were arguably better off with HD DVD technology, which generally cost less to produce, contributing to HD DVD players selling for as little as $99 over the holidays. Meanwhile, Blu-ray players cost about $300 and up -- and movie titles issued in Blu-ray are often sold for twice the cost of a regular DVD."
This is all speculation at this point, as the article didn't confirm that Fox's stance on Blu-Ray was indeed the deciding factor.