images1.wikia.nocookie.net/dragonage/images/8/80/ThedasMap.jpgLet's seeeeee, bottom right is a small piece of land called "Ferelden". I highly doubt any other parts of the map will be available through DLC.. As expansions however..
Expansion 1: The Tevinter Imperium & Antiva
Expansion 2: Rivain, Par Vollen & Seheron
Expansion 3: Anderfels & Orlais
The last one looks the smallest in mapsize, but would be sort of a conclusion to Dragon Age: Origins and at the same time heralding the sequel game, which obviously won't be called "Dragon Age: Origins 2", but will be be named "Dragon Age: < something else>. No, it WON'T be called DA:O 2. DA:O is a the introduction to Thedas: introducing the map, key figures and lore.
Seriously, a business plan like this is pretty obvious with the information available. At the same time, each Expansion will have it's own DLC's to improve upon the lore, add side tracks and everything, making Thedas as a whole more "colorful" (in a good way, not in the happy-happy-joy-joy way of turning everything pink).
Many people have noticed that some party members give more of an epic feeling lorewise than the player character itself. This all fits into that scheme, of introducing Thedas. Did you ever consider that the "origins" part of the game name isn't just about where your character hails from, but also to introduce where some main storyline characters for future games come from? I wouldn't be amazed if in future games, the player would be refered to as a historic character, named The Warden, of unknown origin and unknown sex. If given a codex entry in future game, it will probably state something like:
"Not much is known about The Warden. Some say he was a human noble, some say he was a Dalish sorceror. Some even claim he was a dwarf. Regardless, all historians agree that he was a Grey Warden who probably hailed from the backwater country of Ferelden." And then some more yadayada about accomplishments.
So we will be epic after the conclusion of this specific game, not during the game. We will be shrouded in mystery, but at the same time named in one breath with all famous names who are going to (re)shape Thedas.
Now what future games will exactly evolve around I can't say. There might even be some RTS planned, the diversity in styles of countries certainly allows for that much. But the non-player characters we encounter during DA:O, some of whom we (will) even group with, will definitely play a major role in it. The taint makes our PC relatively short lived: many characters will outlive us, simply because of the ticking timebomb in our blood. Soo much to do, yet soo little time.