https://arch.b4k.co/v/thread/443463387/#443463387Tl;dr: Few days after Joker was announced, someone in 2ch talked about a bunch of scrapped Smash characters: Steve, Sephiroth, Hero, Geno, Chun-Li, Lloyd Irving, Yuri Lowell and Sora. Everyone dismissed this back then, but recently, it gained a lot of traction due to some of these characters making it through DLC. Main theory is that this pass is bringing back old scrapped ideas.
http://anago.2ch.sc/test/read.cgi/ghard/1601895454/39This is another 2ch leak, after Steve was announced, it claimed Sephiroth, Crash, Reimu and Kos-Mos would be the next characters.
https://arch.b4k.co/v/thread/507606657/#507611678Not a "leak" per se, but still worth looking at. This wishlist not only included Steve and Sephiroth, but oddly enough, it suspiciously referred to a pair of ARMs characters: Min Min, who made it into the game; and Ninjara, who Sakurai himself claimed to have considered before setting on Min Min.