I love both XCX and XC2 and wish both could have more represention from music, stages, and characters, tbh...
Truth is Rex always had a better shot this go around in my opinion due to timing and popularity. Which is ironic due to the fact that XC2's timing might've been just wrong enough. But long before XC2 released and before the DLC was done for Smash 4, Elma was one of my biggest wants. She still is, but the realistic part of me says that she's just not the first choice from the Xeno series now, and she's unlikely to get in before Rex does if even he gets in. So I swapped over to Rex support for this gen of Smash because I loved XC2 and he's legit the closest thing I could pick to a winner this time to further represent the Xeno series. And I really think he's still a winner.
Even with all the speculation that Rex wont make it.. compare our character to any other Nintendo character that's possible and it's hard to argue that he legit has less of a chance than anyone. That's due in part to just how silly hard it is to predict what Nintendo and Sakurai might do, but there's no denying XC2's popularity and relevance now. There's a reason we got a special mention in a previous direct. Other characters had poor timing for base roster too, but Sakurai didn't go out of his way to mention them.
With that in mind, that Sakurai quote I believe to just be a reiteration of his comment in the direct. I don't see a reason yet to assume it has anything to do with DLC. It might... but I'm not going to give up hope until I'm told the DLC is done. Even if the odds get slimmer and slimmer. That's how Ridley got in this Smash. Even as he was given boss status and Sakurai said he wouldn't be playable in Smash 4, he came around for Ultimate. Considering the development cycle, he was planned to be playable in Ultimate as the DLC for Smash 4 came out. That's pretty tight timing from saying Ridley wasn't playable in Smash to developing him for Smash, heh. Now, I know that's two different Smash games. But I'd argue that Rex's "deconfirm" has been light so far. We've said it many time in here, but spirits are highly editable and aren't a deconfirm in the same vein as say a boss hazard or AT and as we've also said.. Sakurai saying Rex wouldn't be playable in the base roster doesn't imply anything about his DLC chances. Imo, if Rex doesn't get into this Smash it wont be because of his spirit and it wont be because he's got a mii costume, and it remains to be seen if Sakurai really did imply all instances of DLC when he said Rex didn't make it.
Also, I'm not even thinking about next Smash. The current one isn't even 2 months old and the Switch looks strong as ever. If anything, I can see us getting DLC for a while to come and the next Smash being more than 6 years away. And in 6 plus years, I'll still love XC2, but I'll understand if Rex isn't considered a realistic character to include in Smash, assuming he doesn't slip in as DLC in the meantime. So far the Xeno series has only gotten Shulk and I'm not sure it'll ever reach the representation status of Fire Emblem even if it begins to become a flagship series of Nintendo of near equal standing and popularity - (and it's seems to be pushing in that direction with XC2's momentum). I'd sure love if it did tho... got FE like representation. In my ideal "pie in the sky" scenario... not just Shulk would be playable, but characters like Fiora, Elma, Nia... even KOS-MOS. Maybe even some bad guys like Malos or whatever. This series is quality imo, and the more there is the better in terms of representation.
This all said, I'm hopeful for Rex and not anywhere near giving up on his chances... but I'll also not be that surprised if he doesn't make it. Just based on odds alone. Sure, maybe there's not a lot of main characters in recent popular big Nintendo games unrepresented in Smash... so by that category he should have a great chance. But Smash can do whatever weird thing it wants. We might get characters we've never seen before from unreleased games as Smash DLC. We might get iconic third party characters as DLC. We might even get indy representation as wild as that sounds. Depends on what Nintendo cares to do. I think ultimately they're looking for something that creates hype and makes them money while also being workable by Sakurai. Third parties are pretty strong in that regard and rumors of leaks have implied as much. But we really can't know what's up until it's all released. As far as new popular Nintendo characters tho... Rex is in a top tier league in terms of inclusion chances.