Dragon Age fans have spent years wondering when the mysterious Dragon Age 4 will make its debut, let alone be announced by developer BioWare instead of just teased. However, it's possible that development has taken quite a while in part because there are some plot hurdles that BioWare must clear in order to build the game.
In previous Dragon Age installments, key decisions haven't had a huge presence in the games that follow, in order to allow for as much player agency as possible. It could be assumed that the same would be true for Dragon Age 4, but the key decision in question is quite a large (and seemingly unavoidable) one: it concerns how the players dealt with the mage rebellion in Dragon Age: Inquisition.
Inquisition's Mage Rebellion
Dragon Age: Inquisition saw players dealing with the fallout of a mage rebellion; mages grew fed up with their poor treatment from both templars and the Chantry and decided that it was time for the Circle to become independent. In Inquisition, players then had the choice of either helping the mages or the templars, and whichever faction wasn't helped fell under the control of the game's main boss, Corypheus. Therefore, the decision of how players handled the rebellion is twofold: whether they helped the mages at all, and then how they treated the mages if that faction was aided.
Choosing to help the mages yields the quest In Hushed Whispers, and at the end of it, players can choose to ally with the mages, or arrest and conscript them into helping the Inquisition. How things look for the mages of Thedas would vary wildly based on those choices, and leaves a lot of questions surrounding how Dragon Age 4 would deal with the wide variations in player choice here. However, this wouldn't be the first time BioWare has allowed players to make large, dramatic choices in one game and then skirted around those choices in following titles to allow players just as much freedom then.
Player Agency in Dragon Age
To get a sense of how BioWare has avoided key decisions before, just look at Origins and Dragon Age 2: darkspawn had almost no presence at all in 2, which was a little surprising after the huge decisions regarding the Architect made in Awakening that players still haven't gotten to see the full consequences of yet.
The only times players encountered darkspawn at all was Hawke's trip into the Deep Roads in search of treasure, and that wasn't actually about darkspawn; they were merely the enemy of the moment due to locale. A slight mention of the Architect can be made by Nathaniel in a mission during Act 3 of DA2, but players don't really learn anything new because of it.
Then, there's the key decision of Dragon Age 2: whether or not the players killed, spared, or exiled Anders. It seemed like a big deal at the time, but almost no mention of Anders was given in Inquisition outside of Varric and Hawke, particularly if Anders was romanced. Players who let Anders live still have no idea what he's been doing for the past several years in the gap between DA2 and Inquisition, and then during the events of Inquisition itself. BioWare carefully avoided those past decisions in order to give players as much control over the events in all of the games as possible.
Dragon Age 4's 'Secret' Weapon
Spoiler alert: Dragon Age 4 will, in all likelihood, take place in Tevinter. It was one of the biggest DA4 hints offered in Inquisition DLC Trespasser, along with the knowledge that Solas may be an antagonist in the next Dragon Age game as well. Still, setting the game in Tevinter is a fascinating idea on several levels, and offers one major advantage concerning the decisions made in Inquisition: those decisions may not have as big an effect in Tevinter as they do elsewhere.
After all, Tevinter isn't part of the Chantry like the other countries of Thedas are, and its Circles operate independently. So, while the mage rebellion shook Thedas to its core, the one place where it'd have the least effect (aside from Par Vollen and the Qunari) is in Tevinter, where mages really don't have much of a reason to rebel. Sure, the players' decisions regarding the mage rebellion will have to be acknowledged at certain points, as most past player decisions have been to a small degree, but Tevinter won't be recovering from the rebellion in the same ways that other countries will be. Thus, those decisions don't have to play has big a part in the game's main plot as they otherwise would.
As far as fans have been able to tell, the main struggle within Dragon Age 4 will be Solas' bid to tear down the Veil and recreate the world of the ancient elves, restoring his people to their former "glory." Meanwhile, what happened with the mage rebellion will likely manifest in a couple different ways: whether the player went to get them at all, or abandoned them to Corypheus, whether they were allied or conscripted, and which Divine now commands the Chantry. However, should the game take place in Tevinter, there will always be a degree of separation from all that. Surely mages will have a part in stopping Solas, but being based in Tevinter, players probably won't have to confront their Inquisition choices outright to gain mage support.
Looking back, moving to new areas of Thedas seems to have been BioWare's strategy in previous games, too; the series didn't return to Ferelden until Inquisition, some 11 years after the events of Origins when everything could be different, and players wouldn't be looking around every corner for the consequences of their choices in Origins. Similarly, there was no Free Marches in Inquisition, only mentions through Hawke, Varric, and the war table. It's a strategy that has worked before, and hopefully, it'll work again in Dragon Age 4.
Dragon Age 4 has been confirmed to be in development for PS5.