Second off, I don't want to give away too much, but the release of Mists of Pandaria and what you see in beta is just the beginning. Like any expansion we've done before, you can expect a patch (or two etc.) that continue to move things forward. The launch is about learning about Pandaria, what the intrusion of the Horde and Alliance (and their conflict) means for the land and the denizens within it. That would be the "explore" and "adventure" portion I mentioned. It would also seem a bit odd if that was all we focused on in Pandaria given that we don't need to go to a new land for there to be conflict between the two factions, right?
Maybe I'm thinking too grand here (is there such a thing?), but I am really hoping that a restarting of the conflict is just that. Not a minor plot point in the grand scheme of things, but the major focus of the expansion. I'm talking along the lines of WC1/2/3 here. I want to see cities destroyed and/or changing hands. I want to fight along side big name heroes, and ultimately see some of them die. Not big names you only recognize if you read the books, but people we'd recognize in game.
If when 6.0 rolls around for beta testing and the world looks pretty much exactly the way it does now (every horde/alliance city is still there and owned by the faction that currently owns it) I'd consider that a failure. At least from the standpoint of a new war or even just a re-ignition of the conflict.
I understand there is some difficulty in making that work in a MMO type of video game. People are attached to these heroes and cities. There is also the issue of how it affects the leveling experience, etc. But should that really scare you away from would could be an awesome experience? I don't personally think so, but I don't claim to speak for the masses either.
I'm sure the game will be fun regardless of how it turns out. I'm just hoping that renewing the war will be just that. Not something we look back on 2 years from now and the only thing we ultimately have to show from it is Theramore's destruction, a new Warchief, and panadas.