When I bought the first Appearance Pack, I did it solely because I thought it was worth the price to fix Garrus's armor.

However, I was disappointed that both Jack and Thane were forced to wear those shades -- they are probably the two characters that express the most through their eyes to start with. Anyway, Appearance Packs don't really interest me. It's really no content, just a visual change.
I wonder if Bioware has finally covered every base with their weapons packs. I guess I wouldn't mind them releasing the Blackstorm. I really preferred it when we got a weapon as part of another DLC, like the Locust during Kasumi's mission. For instance, the geth shotgun would have probably made sense if you found it during Overlord.
Not keen on a Romance Pack. For one, the romance pack would have to be designed such that the six possible romance options can be interchanged with each other. I don't think a lot of people take this into account, they think the romance pack will somehow be tailor designed for their preferred love interest. Also, there are other characters on the ship, okay? I want to spend as much time with them as I do a love interest. So more like a Characters Pack. Something that lets you spend time with any squadmate and get to know them better. But honestly, something like that could be integrated with other missions that serve a better purpose to the overall story. Should Bioware want to play for twelve voice actors on a DLC.
Many people will groan, but I would like to see the developers finally get the Hammerhead right. If they release another DLC that uses the Hammerhead but don't make any changes to the vehicle, then forget it. But it just seems if they could somehow meld the Mako and the Hammerhead together, it would be my perfect vehicle.
For actual DLCs that I'd like to see. Kaidan/Ashley DLC. More than anything. Would think it would have to be a DLC that starts to bridge ME2 to ME3, though. Something that brings Shepard back to associating with the Alliance and Citadel space. Also, after
Retribution, I'd think Anderson would also be a candidate for that type of DLC.
Team up with Wrex! Urdnot Clan faces heavy opposition, and Shepard is there to take on all of Tuchanka with the old Krogan Battlemaster. Though don't know how that works for anyone who doesn't have a playthrough with Wrex, especially considering the default doesn't have him. Drat, come to think of it, don't think a DLC with him will ever get made.

I don't think we're done with the Protheans yet. Or actually, with any ancient civilization that had gone up against the Reapers. I would think that maybe some of those civilizations came close to saving themselves, but failed for whatever reason in the end. Like the Protheans and the Conduit, these civilizations would try to leave something behind for the next civilization to use instead. And Shepard needs to find it.
I am
done with the Cerberus DLCs. Fine, you were forced to play ball with them in ME2. Some people even did so quite willingly and are definitely allied with Cerberus from here on out. But I am not. I want Shepard to have the option to work closely with somebody else. For instance, a Rachni DLC. An Alliance DLC. A Hanar DLC. Any mission dealing with some organization other than Cerberus.
The Normandy Crew DLC. Shepard has taken all twelve squadmates out for pizza again and something dastardly happens to the Normandy or near the Normandy that the regular crew of the ship must handle on their own. You play Joker who must command an elite squad of... Ken and Gabby. Or Hadley and Hawthorne.
Okay, I'm done coming up with ideas now that they're heading into the bizarre.