I'm thinking of trading it in since i have almost all the achievements except for the DLC ones (i beat the naked city one cuz it came w/ my preorder) Is it worth it to save it for a little while longer and get the DLC's or trade it in towards the new Batman game?

It depends. I think not because it is about the same set up as any other case in the game: go to scene, find clues, interview, and then solve the case eventually. Of you want more achievements, then it's good for like 300 if you do all of them. But if you decide on them, get the rockstar pass. I think it's like1200 for all of them plus some suits and a kind of gun, ulike separately I think the are all 400.

Trade it in and get Batman AC its really good.