Oda usually do his arcs with themes( Zombies, Angels(skypeia), fishmen etc.) Odas theme basis for the upcoming arc will be Lewis Carrolls books "Alice's Adventures in Wonderland" and "Through the Looking-Glass". In my opinion Oda has already given us a lot of hints..! Here are a few parallels that I have noticed so far: Big Mom- bears many similarities to the Queen of Hearts, including:
-A very quick temper.. is very fast to sentence people to death.. -A great love for sweets.. -Queen of Hearts' subjects are mainly animals.. (SMILE armies..) -Big Mom is also fond of tea parties which feature prominently in Alice's Adventures in Wonderland.
Underworld - Wonderland. In the books, Wonderland was accessed via a rabbit hole and seemed like a strange underworld.. Playing Cards - Alice's Adventures in Wonderland uses playing cards as imagery throughout the story..
The sequel Through the Looking-Glass does a similar thing using a game of chess.. Gigantism via food - Alice inadvertently eats cake which causes her to grow to giant size.. as the kids eat the candy.. There is also a drink which causes Alice to shrink, and a mushroom which also affects size.. In Carrolls books, this also relates to position in the food chain and fear of being eaten, which could obviously relate to Big Mom..
Law- Could easily be compared to the Knave of Hearts, who is later made to stand trial for stealing the Queens Tarts ( stealing the supply of SMILEs from Big Mom..?)
Doflamingo - The Queen of Hearts plays Croquet using flamingos in place of mallets..
Buffalo - Looks very much like the grinning Cheshire cat with a floating ability..
Bobbin - Looks quite like Tweedledum or Tweedledee..
Pekoms - Seems quite similar to the Mock Turtle, who is seen with a Gryphon (which has Lion parts too..)
Tomago - Alice meets Humpty Dumpty in Through the Looking-Glass...
Three eyed girl-Alice?
Props goes to M.o.d.d.