Source: The Wrestling Observer Newsletter
While the reason for the change is not known, one reason may be that they may be changing roles and that The Rock will represent Vince McMahon but that is not a guarantee. Another reason is that the Austin scenario was never a lock and just a hope by some in WWE creative.
The original direction would have seen Vince, Stephanie and Triple H unite at SummerSlam before splitting up again later in the year with Triple H making a heel turn. Now things look to be heading towards a slower build, with the culmination still being at WrestleMania 30.