My theories:
I think the delicious last chapter would be a next episode of cuphead that is unlocked after beating the main campaign, I think the story is that Elder Kettle decides to go on a vacation with the cup bros after the defeat of the devil and decides to use his old boat to travel to his freind Chef Saltbaker who announces the opening of a new restraunt which attracts some former debtors (possible Grim Matchsticks, Baroness Von Bon Bon, and Sally Stageplay)
When entering this establishment we learn that Saltbaker lost the ingredients to his Delicious Last Coursefrom his rival Chef Pepperbeard who wants to make a monopoly on the island's cuisine, the boys decide to collect those ingredients and learn of various locations of rare ingredients, however Pepperbeard learns this and tricks the locals into thinking the boys are criminals and the bosses are trying to stop them from stealing there ingredients.
How Ms Chalice comes in is that Ms Chalice gets trapped again in a mausoleum but this time the ghosts trap her into a tiny teacup that is too small to escape and so she decides to possess it and becomes a third playable character.
From what I saw in the trailers It says that there would be new weapons and charms and i theories those items would actually be sold by King Dice, due to him losing he became in debt (the money kind not the soul kind) and decided to set up shop in this new island, in exchange for some new currency esclusive in the island (possible orange colored) he will sell some new charms and weapons. Here is what I personally want:
Weapons
Peirce Spade: A sharp black bullet that is slow moving but can hit multible targets and hit bosses multible times.
Heart Floater: A magenta heart that gradually floats up, its stronger to make up for the awkward range
Club Blast: based off the unused Exploder Weapon, it is more powerful the farther it goes but it's super will damage you if not careful.
Diamond Ricochete: This purple diamond bounces off walls and gains more power the long it bounces around.
Charms
Sandles: Higher jumps and longer dashes
Muscle Protein: can gain a hitpoint by getting parries beyond the maximum cards
Pop Rocks: creates a small explosion when hit that smashes enemies
Pink Paint: can parry non pink projectiles a maximum of three times per fight.
Another mechanic I want is that the three characters have different strengths and weaknesses while also having the option to have typical cuphead physics.
Cuphead: the same as he was by default
Mugman: weaker attack but faster speed and card filling
Ms Chalice: double jump but slower card filling and shorter dash
Personally I dont know what the bosses are but I theories the DLC will have 8 bosses and 4 run and gun levels. I do have some cool ideas though
Run and Guns:
Culinary Chaos
A giant kitchen that features fire breathing pots and living food over boiling grease, features levitating plates as platforms that you need to ride.
Winter Wrath
A snowy forest leading to the snow boss from the trailers, the stage features ice physics and evil rabbits, deer, and snowmen gangsters.
River Rovel
A flooded forest stage, there is a unique mechanic where the bottom half is filled with swim able water that makes you slower but jump higher.
Scrapyard Scuffle
A garbage dump featuring evil machines mistaking you for trash. Has some conveyer belts and magnets as obstacles.
So far for bosses it seems that they have a theme of a boss controlling a specific part of the enviroment (there is living mountain and show golem as a boss) so I would think we should continue that.
Bosses I want to see:
A giant squid that is fought underwater in a plane.
A sentient sun and moon that trade spaces.
A demonic tree
A flaming ghost woman
Anything your theorizing about this dlc