They didn't always use hubs? I haven't played any Bioware or Obsidian (when they were Black Isle or whatever) games prior to Kotor so I don't know of any other way one of their games could be. The earliest hub game I remember playing is Secret of Monkey Island 2 so maybe they picked it up from LucasArts through Kotor. I can't imagine that they hadn't used it before though.
Well Fallouts were open world, but otherwise, I don't think they did, no*. Like in Torment, 1/3rd of the game took place in Sigil, which had several maps but it wasn't a hub. The maps weren't areas with different subplots that furthered the main plot a little bit. In NwN you had Neverwinter with 3-4 areas each with a spell component and a reason for local disorder.
*Thinking about it, every Bio that comes to my mind was hub based, except the open world BGs.
To be on topic: will there be small sub areas, like the Museum or the Mansions in VtM: Bloodlines?
For instance, Mike gets some info in Moscow, and decides to do a quick break in into the Pentagon?