I think the Austin era still happens. They laid the seeds for the Austin/McMahon storyline before the Montreal screwjob ever happened, Montreal just escalated the hate for Vince faster. Austin was already stunning authority figures well before all of that and was white hot for it. Bret would have eventually given the reigns to Austin because, if I remember right, Bret has said numerous times that he knew Austin was the future (and also pegged The Rock to be a big thing).
In the "Vince chooses Bret" timeline, HHH probably loses a fucking ton of his backstage power due to not having HBK anymore, probably never marries Steph, and (maybe) never reaches the top of the card.