Honestly, I'd say trade it in. Even though I have been a staunch defender of this game for the last month, I finally broke down and traded it in today. I got $27 for it. Nothing great, but apparently I could have gotten more if I traded it in last week, so the price is dropping.
As for DLC, I haven't heard of anything on the horizon, and even if something significant is released, you can always just rent the game to play it. At least that is how I am looking at it. --- "Freedom of speech isn't about protecting the speech you like, its about protecting the speech you hate" - Larry Flynt
Judging by the activity here, I dont think the game sold very well, according to vgchartz (not the most reliable source), 0.17m, Dunno if that would inspire any DLC in the near future, which is a shame as its a pretty good game.
I think many read the reviews and saw ~5 hours gameplay and walked away, but the game is longer than that and of course you have vendetta and NG plus.
I'm glad I got it and its a keeper for me as it finishes off the storyline sufficiantly for me, I will definately dip in and out of the game for a long time. --- Opinions are like testicles. Kick them hard enough, it doesnt matter how many you got.... -Varric