As strange as it sounds, I think at this point Kosmos is just going to be a permanent character in speculation from now on. Not talking just about DLC here, but as in future smash installments included.
Many people gloated that she was just a fad propelled by trolls and fake leaks, and while conversation did die down for a while (hey, that December was ****ing painful), here we are a year later. I see more people that I would never suspect saying things like "I would be ok with her" or "I can see her happening". She placed in the top 50 in that Sourcegaming megapoll this year, which might not sound great, but it's damn crazy when considering this character wasn't even registering before. When I watch prediction videos from Japanese youtubers or nicovideo, they actually include her in their videos. Unlike characters like Elma and Rex people can't just throw the recency argument at her because that's not where her fanbase and arguments for inclusion come from.
I said this in a post in the speculation thread, but the smash community is effectively stuck with us now. Because Monolith is a part of Nintendo now and they already got their foot in Smash. It would be one thing if Nintendo was actively opposed to them referencing their past work, but it's abundantly clear with XB2 that's not the case, not like it wasn't clear from the moment Iwata told them to call Monado XENOblade instead. Now this year we got Future Connected, that, even though it had no Kosmos it gave us even more blatant throwbacks with the Gnosis King and the Shulk Effect, also the Kosmos:Re figure co-owned by Nintendo themselves. And who could forget the chad powermove from Monolith of putting her front and center on their website for the anniversary of the company?
And it's not just Monolith. There are still enough fans out there to justify selling merch of her on the first place. Her announcement for XB2 got more retweets and likes than any other, eclipsing even the guest characters from the other Xenoblade games. The fans are still there almost 15 years later. It's honestly a bit crazy to me.
Even outside Smash I see more and more people in the western Xenoblade community looking fondly to the past. I noticed recently that in the Xenoblade subreddit they added tags for Xenogears and Xenosaga, since people wanted to discuss those games in there. I've also seen the Xenoblade wiki start a discord called Xenowiki that they share with the Xenosaga one, although I don't know the details. In imageboards like 4chan all xeno games are discussed (and ****posted) together as a matter of fact. One XB2 speedrunner I know, Enel, who has like a billion guide videos on youtube and is assisting Chuggaconroy with his XB2 let's play, has started his own let's play of Xenosaga and plans to speedrun the games in the future.
I don't know. When I look at how things are, how things are progressing, I can't imagine a world where if she doesn't make it in this game, that she won't be in a good chunk of speculation for the next one. And with speculation comes support of course, which Nintendo and Sakurai pay attention to.
I'm not sure about where I wanted to go with this. Be hopeful about the future I guess. Don't stress too much about it, things are looking pretty alright, all things considered.