Now most of us know that it was back in 2001 when Triple H got hit with his first torn quad to be specific he got injured on May 23 episode of Monday Raw. The significance of this show is that 1 week later would be the start of the WCW/ECW Invasion. Heavy rumors during that time suggest that Vince wanted to keep both companies active giving WCW it's own show on a different night and channel. Vince would even take this idea far enough to shop WCW programing to networks and almost got it on a Viacomn channel but with three WWE shows they didn't want another wrestling show on their docket. The rumors also suggest that if this got off the ground it would've been very close to the brand split we actually got.
However, a lot of people point to Hunter's injury as the defining moment for the angle and think that they rushed to change plans because of the injury and how the future plans were patterened out. The television thing is actually true, because that is the reason why WWE took so long after the Last episode of Nitro to begin the Invasion as they were trying to find a new home for WCW to keep it on TV.