I know people are still sore about Isaac not being playable, but Golden Sun actually got a lot in Ultimate.
We didn't just get an assist trophy, we got an assist trophy that was taken out of the last game specifically added back in, we got a Mii costume, and we got a bunch of spirits. The only explanation for this is that Isaac, as we all suspected, actually did really well in the poll.
It also leads me to believe that the only reason Isaac didn't get in as a playable character is that Golden Sun hasn't had a game in a while and there's no information about any future titles. Sakurai has said in the past that he prefers active franchises and recognizable characters. Even when talking about Piranha Plant he specifically said that one of the reasons why he added him was because he was recognizable and thus a better choice than main characters from lesser known franchises. (And, if there aren't any Nintendo characters left from active franchises, he's more than eager to fill the spots with 3rd parties instead of mining Nintendo's back-catalog, unfortunately).
So, what does this mean for Isaac's chances for the next Smash? Pretty much, unless Golden Sun gets a new game (and the development/release happens to be in the right time-window of the next Smash's release) or someone else besides Sakurai directs the game, he really doesn't have a chance of being playable. Which kind of sucks. It just confirms the idea I've always had that Isaac is a perfect character for Smash but just got unlucky with his timing.
But, I won't be too disappointed this time. We got a a more fleshed out assist trophy, a costume, and pretty much confirmation of his popularity in the Smash community. I would've liked some more music, but we did pretty good overall for Ultimate.