My guess is that any DLC pack going forward will maintain the Fighter Pass design, so a character, stage, and music tracks.
As we’ve discussed before, it seems that the absence of Spirit events for Astral Chain and Three Houses might suggest something is up. If Sword & Shield meet the same fate, it’ll probably add more fuel to the fire.
While I don’t know that 1st parties will be a focus, I think those three games/series will have the best shot at getting the nod. I think the MC of Astral Chain, Edelgard, Byleth, or even a surprise Zacian pick for Sword & Shield would bring something new and cool, and I would never be against something like that as long as it oozes character with the inclusion.
Even if I think there’s more to gain from expanding the 3rd parties available, it’s not like a 1st party pick is bad by virtue of being owned by Nintendo. I think it just comes down to the vision for the game, and the fact that everything so far has been entirely new (not just the characters, but the series coming in as well) to Smash. This is mainly why I would be happy to see Edelgard and/or Byleth, but don’t know that “Fire Emblem” really has that “new” feel to it.
I’m open minded, really. I probably don’t seem that way, but just because I prefer the “most if not all 3rd parties” route, I’m not totally against Nintendo picks. I just think 3rd party additions make it really an unbeatable crossover, adding the likes of Crash, Leon, Dante, Heihachi, Lloyd, and many, many others.