IMO for a good ending to DC, you'd need 100 years of peace... or maybe 1000 if the Dragon Commander stayed involved. After such a 'golden age' things could go back to normal.
I would assume he ruled for a while, either directly or as more of a figurehead / adviser. After the empire (or republic, depending on the political decisions you make in DC) was up and running, presumably he would eventually withdraw from politics to concentrate on more interesting things, or just start to take on more of the dragons' non interference attitude. When the empire started to decline, I could see the Dragon Commander simply not wanting to get involved, let alone not wanting to go to war. With 8800 years, he could even come back a couple times to restore the empire before giving up on the seven races. If the government transitioned to a democracy at some point, then the Dragon Commander could have come to believe that democracy is the best political system, not because it allows people to choose their leaders, but because it gives people the government they deserve.
