I don't really think it matters that Golden Sun hasn't had a game since 2010. That's not a terribly long time compared to some other series that have been waiting forever. I mean, if the Mother series can have two reps, then by god, anyone can have at least one. And I say that as a huuuge fan of the Mother series. Isaac mostly has had an uphill battle due to the fact that he's in that awkward in-between; he's not quite new enough, but not quite retro enough either. Pit and Little Mac got in a lot easier despite having very few entries due to the fact that they were very retro. Isaac's support is mostly running on the steam of people who know that he has unique abilities and that his games were really damn good.
On the note of Wolf, I'm a bit more open to veteran characters myself, due to the fact that they actually took a terrible, terrible character and made him playable- Roy, that is. However, at this point it's pretty much limited to just Wolf, since I don't really want anymore Pokemon (I mean, especially Pichu, who would've been added from the start anyway if it had a shot of getting in, considering Dr. Mario, Lucina, and Dark Pit), and despite being a huge Zelda fan, Young Link doesn't appeal to me because we have two Links and I'd rather get someone brand new, like Tetra or Impa. Wolf was pretty fun in Brawl, though, with his much more savage style, so I'd like to see how he'd possibly further get Luigi-fied.
Obviously, as long as we get Isaac, though, I'm not too concerned about the others. K.Rool, Dixie, Shovel Knight, Shantae, Chibi Robo, Geno, and a few others I'm sure I'm forgetting are all pretty great as well and have my support. I'm not too picky, apart from a couple characters that I think would be uninteresting.