I'm personally fine with my Warden being off doing other vague things somewhere far away from the plot. Let me headcanon in my own details and that's enough for me. Better than bringing her back and changing her drastically from my "vision" of what she should be. Same with my Hawke (and, I suppose, my Quizzie in the next game, depending on how Trespasser ends). The only reason I wanted them in Inquisition, honestly, was the vague "they have mysteriously disappeared!" ending of DA2, but then that turned out to all be coincidence anyway, so now there's no need for the Warden to be part of the story, though.
Hawke does probably need to come back one more time, but just so we can set her off in an "around, but not involved" way as well, since Inquisition didn't really do that. And once that's done, I never want to see another main character reappearance again (unless that character ends up reappearing as a controllable main character across multiple games, I suppose). Referenced is fine. Directly involved should be a no-no.