In terms of blank slate, I guess it's true they really should not do much setting things in stone as that would ruin differing perspective. I'm hoping more though that there would be some stuff that would centre on the WoL and you would have options to deal with these events that suits the way you want your character to be?
In the style of Old Republic (though I left that game years ago for various reasons I'll always give it points for letting you have near total control of your character's behavior in the game, you could be a darling angel or you could be a mean ****tard!) or even Elder Scrolls Online, there could be a bunch of events where you have the option of reacting in a certain way, the way you want to which could change the way NPCs behave around you or even change the nature of some quests