So far it seems that way, at least for DLC 5 (things might change later on).

Many characters have been deconfirmed by several leakers, specifically Vergeben and Sabi, both with good enough track records (Vergeben has had some stumbles recently but he knew every character on the base game + deconfirmed Grinch leak + knew about a Dragon Quest rep..., Sabi on the other hand leaked some much stuff they got a cease and desist letter from Nintendo themselves at E3 lmao)

Ryu Hayabusa (Ninja Gaiden), Dante (Devil May Cry), Crash (Crash Bandicoot) were deconfirmed by Sabi. They also said that if the Geno and Doom Slayer Mii Costumes were real they had nothing to do with DLC 5, esencially deconfirming them as well.

Vergeben has backed some of this as well (like Doom Slayer or Geno), but he also deconfirmed Gordon Freeman (Half-Life), Scorpion (Mortal Kombat) and a Ubisoft and Falcom rep.

Again, all of this for fighter 5, we don't know later on.