I thought there was some talk about having a more open world? Id look for it but I'm on my phone. Now I know there is transiting but I'm pretty sure I read some where that the world is suppose to be a lot more open.
In regards to more open, I believe there was talk of more than one home base/city in each act, but that is not confirmed. Beyond that though the acts will be completely segregated as Scyber was saying.
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If that made sense to you, Bravo! I think I even confused myself...
From what little I remember of Blizzcon 2008-2009, the open world is not randomized. Only dungeons are randomized. I think that's what you are confused on with the term consistent world.
With the entire world being not randomized, you know where each land is to look something like Azeroth. No matter where you are or where you go, you know the land and where each zone is, or where to take the zeppelin or the boat.
In Diablo II, the open world was randomized too -- so it was kinda hard to remember where to go to find X or Y place or dungeon entrance.
Edit: I should mention the quests on the open world are randomized, not the environment itself.
It would be awesome if each act had a more open feel to them (more to explore). I also hope they incorporate areas that lead nowhere, just for extra fun. (Kind of like Diablo 2 where if i remember correctly, their were two different paths to take in act one, where won would lead you to Bloodraven and another just to some 'off the main track' area).