You're still getting a little ahead of yourself if you can actually bring down Orlais or restore the Dales. The preview doesn't really say much.
Some of us have read the larger preview of "The Masked Empire", and are hopeful that an elven plot will exist in Inquisition. Letting the Orlesian Empire fall apart would simply be a bonus.
Also Shartan was killed in another part of the world before there ever was a Dales, he's only indirectly related to the Exalted Plains.
To an extent. Having a homeland of their own was still the dream in Shartan's time, and his leadership of the elven slaves he lead to freedom, and then against the Imperium, made that homeland possible.
As the History of the Elves reads, "The rebellion was brief but successful; the death of the prophetess did not end our fight, and we fought on for independence even as the human Imperium began to crumble. In the end, we had won freedom and the southern reaches of land known as the Dales.
"It was a home, a new chance to gather and rebuild all that we had lost. In our centuries of slavery we had lost our immortality, our language, our culture, our crafts… but never our sense of belonging to each other. From across Thedas we came to the Dales. We walked on foot, sometimes crossing thousands of miles with naught but our will to sustain us. Many of us perished on the Long Walk, but those of us that arrived at our new home were all the more determined.
"There, in the Dales, our people revived the lost lore as best they could, and even turned to worship the old gods in their ancient prison. They called their first city Halamshiral, 'the end of the journey,' and founded a new nation, isolated as elves were meant to be. They created an order called The Emerald Knights and charged them with watching the borders for trouble with the humans."