I don't think it's so much an appeal for nostalgia as it is a way of bringing the setting back to a form that it's recognizable for people without much hassle. In my experiences—and although I prefer running games after the Amber trilogy—it's kinda difficult to explain to new players who may have an idea of what Dragonlance is, be it from prose fiction, old gaming materials, comic books, etc., how much has happened in the world in the last 60-70 years. Heck, we even had a Second Cataclysm!
For hardcore fans of the setting who are up to date it's no problem, but it really becomes a challenge when trying to introduce new players.
I do think that you're right about your prediction that the trilogy will be centered on the "careful what you wish for" theme, but I do believe that we'll end with a new Post-War of the Lance, with the classic 21 gods, only one type of Kender, only the Knights of Solamnia, etc. I think this is the best option for a Dragonlance revival because a) people could be onboarded from other media more easily and b) it allows for those who love stuff from the no longer canonical future to incorporate them a la carte. The best of both worlds, in my opinion.
I don't disagree with you largely, other than pointing out that the setting having a lot of stuff happening in an unrealistic time period is nothing unique to Dragonlance. I mean there have been just as many world altering disasters and gods being created/killed in Fae'run too but no one seems be clamoring to simplify or retcon literally 2.5 DECADES (our time) of the setting. The only real difference between the two is that WotC has been actually actively supporting Fae'Run.
Where I disagree though is saying that resetting it to the War of the Lance will be helpful for new players. First, it's a complicated setting no matter which time period you set it in, especially during or post War of the Lance, which is a
heavily detailed and documented time period. Anyone who has ever played any of the Lord of the Rings tabletop or has used Middle Earth as a setting is often aware of this issue, primarily with many DMs or players feeling pressured to "stick to the script" of the novels, or alternatively feeling like you're playing second fiddle to the actual events that matter. Sure a skilled DM can mitigate this but I feel like it's far more of an issue than most care to admit, particularly for players with less experience.
Second, and I know this is probably not fun to hear for most fans of the series, but there are two things most need to realize: a) most people under the age of 30 have never even
heard of dragonlance outside of the few random offmentions in the 5e books unless they frequent online roleplaying forums, and I'd hesitate to even call the people on this site representative of the majority of the 5e playerbase. I mean heck I have 5 players who are all
avid fantasy readers each with literal bookshelves of different stories and not one of them had even read one of the books that wasn't the first book. I love this series dearly by popular now a days it is not.
Related to this: point b) The original trilogy has
not aged well. What was once revolutionary and genre setting now comes off as cliche, forced, and outright offensive with some of the side characters. While I do agree that social media overblows this as it does with almost everything and that some of it's criticisms are unfair as this series arguably helped create many fantasy tropes, like it or not this is the reality this series/setting faces. The fantasy genre and gaming space have changed quite substantially in 38 years, and it's foolish to think that denying this is good for the longevity of the brand. The setting needs substantial updates to truly bring it up to speed, and we need to acknowledge that neither leaving it unchanged nor negating all but the first three books will fix it. My argument is that simply that if it was to be a false dichotomy of those two extremes I'd sooner keep Age of Mortals in a heartbeat. It's not even a close comparison.