I think it is way too early to say there's any kind of HD-2D fatigue just based on Octopath 2 slightly underperformed the first game in the launch window. It is still likely to be their, what, 3rd or 4th best selling game out of the 20+ released in the fiscal year (behind Crisis Core, Forspoken and probably Theateryhthm?) Saying "worse marketing" really yada yada yadas past the point that the first game was published by Nintendo so SE was getting less revenue per copy sold (how much less I don't know). 20% lower sales but potentially about that or more revenue per sale? Steam looks like it is doing pretty well (seemingly the best PC launch of their entire FY slate by 50% to 500%), and I'm just not at all convinced that OT2 is not going to pass OT1 at some point in a few years. Steam sales look like they are wildly higher than OT1's steam launch, and I think Steam OT2 is almost a lock to eventually pass Steam OT1. Meanwhile, Triangle Strategy looks fantastic if you just look at Switch, but the Steam version really went nowhere despite being by far the largest performance improvement out of the three Steam games.
At this point, DQ3 is coming. If that does well, they will move on to DQ1&2 combo pack. TriStrat, Octopath, and LAL have all done well enough to justify sequels. A new Final Fantasy spinoff in the style seems like a lock, but trying to determine the order for them is a fools game. Nier 2 is one of SE's best selling games at this point (the best outside of their big three franchises), and there's not even any leaks about Nier 3 yet 6 years later.
If there is a remake of an old game, I'd bet on Treasure of the Rudras, for being a never-officially-localized SNES game with multiple protagonists and an intertwining narrative, which is on-brand for Asano's interests. Bahamut Lagoon