I agree with you OP. I hope for open-world areas/content unlocked through progression of missions or quests. But, I also agree with Hulan in that it doesn't really seem like the direction ARR is headed. I would expect more along the lines of what we've already seen.. similar to the content experienced in MMOs like Rift and WoW (heavily heavily heavily instanced, with some focus on open-world content), at least as far as this year is concerned. If ARR lasts for at least a good couple years it should get some decent expansions that I'd hope will start to incorporate a more open-world and dynamic feel to the game.

There was a thread started by "ThePatriarch" (iirc) that went for a lonngg time addressing this somewhat. It was moreso focused on all open-world content, but your storyline open-world area suggestion would also work perfectly for that thread too. It used to be reviewed by the mods, idk if they still do though (although they should... ARR could still definetly use alot of the suggestions in that thread..)