Okay on 1 side
We have
Kaido
3 calamities
Flying 6
Numbers(at least 9(2-10 ace potentially being the son)
Scratchman Apoo
Hawkins
Headliners
Gifters
Kaidos son
Big Mom
Perospero
Smoothie
Daifuku
Homies
Other big mom kids
Orochi
Kanjuro
Onibawan
Any other orochi minions
On the other side we have
Luffy
Strawhats
Law and heart pirates
Kid and crew
Caribou
7 scabards
Lots of samurai
Some yakuza
Minks
Momonosuke
Benkei
Hiyori
These sides to me do not appear evenly balanced at this stage by far and I am tempted to say that either the initial raid will fail or a change in dynamic will occur.
Basically something has to remove big mom from the picture. This could be her betraying kaido (possibility that this was all a routine setup including the release of jinbe she may potentially have plants as well) she goes to deal with some other unmentioned up until this point force(such as marines, wg or another yonko) or she has to retreat because she finds out something bad is going down at Wci.
So far it is implied that there are some people on Kaidos current side as well who are considering turning on him if they detect an opportunity. These include Hawkins and Drake (Also potentially other flying 6 the theory that the leader is crocodile and that the one wearing the tucked in trousers is Mr 1 could be valid)
I mean the strawhat grand fleet could turn up but I find all of them turning up to be unlikely. However as Bartolomeos fruit originally came from Wano I would find it weird for him to not make an appearance.
Sword might make an appearance. Another Yonko (most likely bb) also has potential. Moria has been foreshadowed to have a vendetta against kaido and would be unusual if he wasn't in wano for kaidos eventual defeat plus he also gives a great potential stat boost to luffy's side.
Also we are expecting nekomamushi to return at some point.
The flying six other than page 1 and drake we don't know who the members are but because of the shown shoes people are hypothesising that there is a samurai a woman a person with trousers which are similar to Mr 1s. And a person who has buckles on their shoes (possibly Crocodile but have also heard gin from baratie). If these characters are as such then we can assume they might fight each other and eliminate themselves.
Kaidos sun could either be a joke character, a kaido clone or a separate well written character with his own dreams and ideals. Only if hes a kaido clone will he truly stay on the beast pirates side.
The theory that hes on his own during the banquet suggests that luffy might run into him 1st.
Curveball theory the woman or samurai could be kuina.