I would love it don't get me wrong. But the size of the early datamine is huge. That would have to be one long ass reveal video to cover everything. And it always makes sense from a marketing sense to divide things over time so as to prolong the hype. And Alpha is NOT early access. It's limited access to very few people. We are all obsessed with WoW here so a very large number of people in this thread makes it into beta and some even get into alpha (personally only missed the Cata beta) but it's still a tiny part of the community. The only case of it working differently was MoP and I don't think that was a successful experiment.
IF there is a revamp though that is meant as new leveling content, I could see that happen, with just that content on it. I could even see Early Access given to some content ahead of the expac by a bit longer so we can be kept busy.