So, I've been thinking about companions coming back in other games and that got me thinking about Dragon Age 4 and what companions could potentially come back, especially then ones that might've not had a lot of love so far.

I think that Zevran could be a great choice. Out of 4 love interests in Origins, he feels like the most shafted one, and given that we are going to Tevinter, I think him coming back would be great. And I mean, like, coming back as a companion. I just think that there are so many ways you can take it: does he come back as an advisor or full-on companion, did he romance Warden or not, so on and so forth. There probably can be a whole thread about Zevran coming back in DA4. (Also, my guilty pleasure Origins playthrough is King Warden with Zevran as the consort of Warden and if that could be referenced in DA4, I would die)

Sten could be a great option too. Since Teviner and Qunari been at odds for gods know how long, DA4 can finally give us a chance to interact with the Qun properly. Not with just some agents (Ben-Hassrath) or outcasts (Tal-Vashoth/Vashoth) but Qun proper: like, maybe some big Qunari camp next to Teviner. And if they will do that, having Sten be there would just be cool and add flavor to the story. I think the last time we have seen him he...helped Alistair merc another Qunari guy? Like, an army commander or something? I remember very vagualy.

No matter how hard I try, I can't come up with a good justification for Shale to show up but I want them to. Shale is just too great, we need to see them again. Doesn't have to be anything major, could be just a side quest after which they go ahead and travel somewhere else: maybe Shale found out that dragons are just "big birds" and we need to assist them in killing some high dragon in Tevinter before they continue traveling.

Not a companion, but Warden is showing up 99%. Like, holy shit, if there were ever a chance to bring them back, now is the time.

EDIT: You know, I thought a bit more after writing this up and want to add something while I have a chance.
First, Architect. If Warden been friends with them in Origins, bringing them together in DA4 would be megabadass. This way, you could cut down on Warden talking and Architect could also provide some amazing commentary on modern-day Tevinter. Also, you know, they are just cool, period.

Second, Loghain. Now, this might be crazy, but we don't really know if the person who was left in the Fade in Inquisition dies. What if Loghain gets to live and gets to come back: once again, we are in Tevinter, that kinda opens up many "mage shenanigans" doors. What if someone, some powerful mage, was scouring Fade one day and just found him there and now Loghain is a prisoner in Tevinter. Loghain dying to protect Inquisitor and Hawke was a nice finale to his story but, if they do want to bring him back like this, it would be amazing too.