I think that in the past, "relevancy" (which is a term I hate to use because in Smash discussion it's always erroneously as a synonym for "having appeared in a recent game") did matter quite a lot, especially in Smash 4 where it felt like nearly every newcomer and stage was tied into some recent and marketable game that Nintendo could advertise. We can argue casual vs hardcore recognition and demographics all we want, but I don't think it's assuming too much to say that Shulk wasn't any more recognizable or iconic than someone like Isaac, for instance. He merely had a more recent game in a franchise with more contemporary value to Nintendo, and that gave him a huge advantage. Obviously, the final decision was Sakurai's to make, but I think he takes that sort of thing into consideration.
However, I think at this point, Sakurai has built up enough credit for himself that Nintendo is more willing to let the man choose content according to his own personal vision, and I expect him to be a bit more unconventional with his picks this time around. It's telling, I think, that we've barely seen any new stages at all, while almost every past stage is returning. A lot of these stages represent old, dated, forgotten, "irrelevant" games, which is a complete 180 from Smash 4's trend of "first level from whatever each series' most recent game is". It might be calling it too early, but the focus seems to be less on the contemporary and more on a comprehensive history of Nintendo, with the content more spread out across a wider range of source games. The Zelda cast all have designs from different games, for instance, whereas in past games, they all tended to conform to whatever was most recent. Returning characters like Young Link and Pichu are hardly "relevant" anymore, but that didn't stop Sakurai from going through with bringing everyone back anyway. Based on past trends, we'd be expecting all the new DK content to represent Tropical Freeze specifically, but maybe that won't actually be the case this time.
While I believe that historically, a character like Geno had absolutely no shot due to being so irrelevant in the grand scheme of Nintendo's history, I now wouldn't be surprised if he actually got in, as long as Sakurai wanted to make it happen. While K. Rool not appearing in such a long time certainly doesn't help him, I don't think his no-show status is going to be the final deciding factor. It's really up to Sakurai and whether he wants to make it happen. If he really has a desire to do it, I think we'll see K. Rool. I doubt he'd get vetoed by any higher-ups, because I really do believe that Nintendo gives Sakurai a lot of free reign over the characters he chooses to include. If Sakurai wants K. Rool despite his lack of recent appearances, I think we'll get K. Rool. If that's too big of a hurdle for Sakurai to get over, then it's still ultimately his call.
I don't place much stock in the fanmade ballot surveys, personally. I think it wildly inflates and deflates people's expectations. The Mii costume, on the other hand, is actual, observable evidence that we can infer from. I think that matters more than any unavoidably flawed fan research.
