PM already has Elvis, Lady Gaga, Tio Sam, Lara Croft. If the trend is to continue like this, we could see Marilyn, Lincoln and others.
Taking ideas from Lego I would love to see: Wrestler in mask (1), Mime artist (2), Sumo (?) wrestler (3), Frankenstein (4), Dwarf clown (5), Irish Leprechaun (6), Aztec Eagle Knight-Scottish with bagpipes-Hippie (7)
With the introduction of new torso and legs used in swimmers, gymnasts and ballerinas the possibilities are unlimited, almost all themes could have new figures with different dresses but I do not think that's gonna happen. At least, Aztec and African warriors would be great.