Since you guys are wondering if there's gonna be any Heartless bosses, the answer is yes! There are gonna be some Soulless bosses.

Darkshadow: One of the biggest Soulless, rather around the same size as a Darkside Heartless. It can pound the ground with its fist, creating dark shockwaves from them. It can spawn Soulless, lift objects with telekinesis, unleash dark energy balls, and can even fly with its wings. 

Champ Matro: Huge version of the Mastro-Squash and acts as a mini-boss. Its first appearance is at the Wumpa Islands of Crash Bandicoot. 

Giant Wildclaw: Giant version of a Wildclaw. 

Giant Squashette: Giant version of a Squashette. 

Giant Depleter: Giant version of a Depleter. 

Giant Magnafowl: Giant version of a Magnafowl. 

Piranha Shaman Plant: A Soulless shaman with a Petty Piranha outfit, and a pot plant with vines underneath it that act like tentacles. Its first appearance is the Mushroom Kingdom of Mario + Rabbids. It can summon plant like Soulless such as Rooters, grab enemies with its vines, and can launch fireballs with its staff. 

Hydra: A large Soulless with multiples heads. Its first appearance is in Olympus Coliseum. It can breathe dark fire from its mouth and capable of regrow more heads.

Mighty Chewy: A giant mechanical Soulless gorilla. He wears golden headphones and has robotic hands and feet. His first appearance is in Ape Escape. He can spit out Soulless from his mouth such Mini-Mons, Voltee(s), and Jab-Jabs. He can slam his fists on down, creating shockwaves. He can even make them by biting down with his teeth. Chewy can also chucks girders at his enemies which can be use as bridges, picks up a chunk of a building and slides it towards them, and can also pick up a giant Ring-Ring and slam it down on the stage. 

Mutant Chimera: A Soulless composed of Mutant/Titan DNA. Its first appearance is in the Wumpa Islands of Crash Bandicoot. It can use any Mutant powers it has at its disposal. Its own abilities are shooting orbs that will make enemies slower, unleash an asteroid from the sky, and create a black hole with strong suction.

If you guys have ideas for Soulless bosses, let me know at the comments below. Peace out and enjoy!