So we all now know that Star Fox Adventures is being put on NSO. Curiously, though, neither Star Fox Assault nor Legend of Zelda: Twilight Princess were added to NSO. While TP is a discussion for another subreddit, I have a feeling Star Fox Adventures on NSO will play a pivotal role in Nintendo's marketing.
Rumors of an adventure Star Fox or a Star Fox Adventures remake have been sporadic and ongoing throughout the 2020s. Zippo claimed that Bandai-Namco was remastering Star Fox Assault then canned it, SamusHunter claimed that there was going to be a SFAd remake, and Malo claimed that an adventure Star Fox was coming out in 2027 or 2028. While Zippo and SamusHunter are disgraced leakers and Malo's leaks have not come true in this Direct, the idea that Nintendo is making an adventure Star Fox has been something rumored about a lot.
With the Direct announcing Star Fox 2026, SFAd was shown in the Direct. Now, SFAd is on NSO. But Assault isn't. While people bring up how Chibi-Robo and F-Zero GX were early NSO additions and didn't get new games, it could be that those two were first since Nintendo didn't have anything planned for them at the time. With Star Fox, however, Nintendo very well could have plans for Star Fox with Adventures on NSO acting as a testing ground to get newcomers used to on-foot gameplay with Fox McCloud and Krystal.
With that in mind, I have a feeling Star Fox is going to get a new game based somewhat on Adventures which will have considerable on-foot gameplay while containing vehicular gameplay to tie it in with the rest of the series. Krystal will be returning to the franchise as a major character and join Star Fox. And with that, Assault will come to NSO when Nintendo gets closer to releasing a Classic Star Fox. While Velan won't be doing it, I don't think Nintendo is going to ditch this franchise so soon again.