Having Aurelion Sol burn away the space parasites and flying off to freedom and creating a whole different story for Targon.
But that's never going to happen, so let's actually get to a serious answer. Personally, I think Riot has a problem on their hands, and it has to do mostly with their pace of releasing lore and their worldbuilding.
So, as I see it there are two different desires that are the focus of the lore. The first is to lay the foundation for the world (there are still champions that are more or less in lore limbo), and to create meaningful advancement in the world. But you can't really have meaningful advancement without first laying the groundwork for what the status quo is. They also have to deal with the perception these locations have built over the last decade or so, however long they are supposed to have existed.
And totally honest, Riot has balanced these issues before. I usually keep bang on about how much I like the Bilgewater update. And I think it did a fantastic job of playing off the various problems Riot had to face to make a satisfying story. Bilgewater needed to be built up as a faction, but they based their build up very heavily on what it was implied to be before the great lore retcon. So a lot of their work was already done. And it shook up that foundation pretty successfully. There was meaningful advancement to the plot of Bilgewater by having Miss Fortune take down Gangplank in a violent coup. Perfectly done. It brings meaningful change to the setting, however, it still stays true to the setting's roots. This is pirate land. These stories are still going to focus on pirate-y things.
Shurima, which I don't think was as successful as Bilgewater still did pretty well. We had quite a bit more set up with Shurima. Changing Nasus and Renekton's backstory from being aliens to being from a once mighty empire was a nice touch. And from their design we all can see the Egyptian parallels. This gets us in the desert and gods frame of mind, which the lore then played upon. We got another glimpse of how the setting worked with Azir release, still hammering in the idea of archeological discovery of a long dead empire with the gods returning to bring prosperity back. The actual big lore event with Xerath facing down Nasus also established a minor change to the status quo, with the villain creating his own empire. But mostly this is all just set up that carries through on the promises of the setting.
Let's compare and contrast this to Demacia. Demacia was always seen as a knightly kingdom of honor, duty, and discipline. Probably a bit too totalitarian. But it was a land of knights and medieval style fantasy. Then the lore retcon happened, and after waiting far, far too long we now have a Demacia where magic is a death sentence, or not, depending on which story we're looking at. But it's still supposedly a land of chivalry, duty, honor, all that good high fantasy medieval stuff.
Only we don't see that. Instead of showing this status quo in stories we just kind of skipped it and went into the mage problem. Now I'm biased here. I don't care about the mage problem. After hearing the pitch of Demacia I had visions of knightly tales of war, tournaments, honor, intrigue. All the stuff I love. But we haven't got that, at all. Every lore event has just focused on the mages and how they're untreated. Which, you know, fair. The medieval world was not an equitable one, by any stretch of the imagination. But as of now the story Demacia is focusing on has to contend with the years of Demacia not being at all related to this stuff before. And that it hasn't really done a good job of establishing the status quo in the first place.
So, my suggestion. When creating the first main story arc for the setting you're on, it's ok to make interesting changes that develop the lore from the complete stagnant morass it has been for years. But the development should be related to the inherent promises of each setting. If a world is pitched on knightly orders and honor. Have the setting be warped along the lines of knights and honor.
If the setting is instead based on foundations of expansionist war and might makes right politics, the great early changes to the setting should focus on that. And with Swain you did just that. Only for some reason that escapes me, instead of having the first Noxus showing the political maneuvers that Swain used to gain power, it kind of picked up right after that point. Bit of a wasted opportunity there.
Anyway, I'm not sure what else I can add in. The only settings I care about: Bilgewater, Demacia, Noxus, and in a sorry negative case Targon, have all had their updates. I have mixed feelings on all of them. But i would suggest, when adding development, make certain that the way the story develops also brings foundation for the setting and makes the lands at least likeable.
I truly believe that the mage problem could have worked with Demacia, if it was the second story. Coming out as the first just doesn't feel right as an establishing story.