I'm glad somebody mentioned Sebastian lol I always saved Anders, I couldn't bring myself to kill him despite being a psycho who made the mage hating situation even worse for everyone tot he point that dai happened, so Sexy!Sebby left to go off to Starkhaven to rebuild. Granted I was already pushing him to be prince anyway and rule but still I'd like to see how that turned out.
Also I'm an avid Gideon Emery lover, I have the hugest crush on Balthier, loved Steve on Tekken, he was even a Candy obsessed thief in the latest Fire Emblem game. and of course he's an obligatary VA on almost every game that has english sounding voices. I even watched Teen Wolf just becuase he was on the show wearing skin tight sweaters might i add. So like a previous poster said I'd just like it if Fenris return, if not for the fact that I love him and him and my male mage Hawke are an angsty rival pair who truly care for each other, but just to hear Gideon Emery speak. My non-existent ovaries would be so happy. I even think that he could somehow work in the plot, be it a stretch, but it'd be cool if Dorian and him had some sort of past. It may be reaching but I'd just love for him to be in it. However at this point, according to Gideon's official Facebook he's said that he hasn't heard from Bioware, so idk. ;_; i'll just hope in the corner.
As for Anders, I love/hate him, love to hate him, hate that i love him, just so many mixed feelings but I'm sure he'll return in some capacity, if alive then coo if dead then probably some abomination/spirited version that fused with Justice since he was killed. Unless Justice found a new host. I always thought it'd be cool considering by the end of Act 3 it seemed like Anders and Justice were now one completely since it drove Anders to do such things and if you do decide to kill him he becomes a Fade Spirit/Demon. Gotta love his VA though.

To help fuel the suggestion that Anders might be in DAI however, there is this to note:

Could it be Dragon Age Inquisition? I don't know, but here's hoping
As for others, I'd love for Isabela to show up mostly becuase I love her, at least in some vein. Out of all of the companions sans Varric since he's already in it, it would make perfect sense for her to be there since she's a treasure pirate who travels the world. I feel like she's more fitted to be the "cameo who appears for a couple of missions and leaves some form of impression" type of person which is what they tried to do with Zev.
Anyway, sorry for the huge post!