I admit that I do want a returning protagonist at least once down the road.
Dragon Age suffers from the same problem that Marvel's super heroes do in the Marvel Cinematic Universe. Once Marvel showed that they were all in the same continuity, making more and more movies with different heroes becomes difficult because they not only have to fit the shared universe, but they must also be contained within their own movies. The longer this goes on, the less logical it becomes, because the cast of all-powerful super protagonists grows and expands, but they rarely (if ever) interact with one another outside one-off scenarios or special situations (The Avengers, in this case). I mean, where is Tony Stark during the second Captain America movie? It seems silly for not a single other member of the Avengers to come and help Rogers while HYDRA and the Winter Soldier are hunting him.
Likewise, since DA has a new protagonist for every game, it's going to become a bit silly when (inevitably) the world is on the brink of destruction (again), and only the [insert fancy title here] can stop it (again). Now granted, the DA protagonists have never teamed up like the Avengers, but they are all major lore figures (and all alive so far, unless you didn't do the Dark Ritual with the Warden) who all live in roughly the same area. I know that the Warden in DAI is off on a quest to stop the calling (which makes sense, given that he is a Warden), but there is no reason whatsoever for Hawke to never reappear (and then re-disappear, as per the epilogue). It's all really convenient for all of the world-famous heroes who saved the world multiple times to all be unavailable when the world is about to end.