Luffy: He’s pretty much at his peak but I imagine he’ll become better at using Advanced Conqueror’s Haki and his awakening. Kaidou says that his use of infusion is sloppy.

Zoro: Black Blades and most likely advanced forms of Haki. I believe Zoro will have better observation as his next opponent will be the invisible Shiryu. Probably better infusion too.

Sanji: Same with Zoro but maybe some increased flame capabilities. Very miniscule chance of getting Conqueror’s Haki (doubt it but possible). The cover of the 100 volume titled Conqueror’s Haki and it has Luffy, Zoro, Sanji, Yamato, Ace, all of them has Conqueror’s Haki except Sanji, so I think it’s a foreshadowing.

Usopp: Kabuto eating a Devil fruit and Usopp will definitely improve his Observation Haki (Future sight might make him too OP as a sniper but I don’t doubt he might learn it.) Possibly a weak form of Armament Haki (definitely not advanced.) If not Kabuto getting an upgrade, maybe some type of hammer from Elbaf (Shoutout to whoever made that theory ion really know who did.)

Nami: Probably at her peak having Zeus and all maybe some extra tech who knows. Nami will utilize her training with Shinobu and incorporate her ninja skill with her Clima-Tact/ Zeus staff.

Robin: She could use Armament Haki in her Demonio Fleur. If Demonio Fleur isn’t her awakening then she’ll probably awaken her fruit. If it is, then she probably just better control over it.

Franky: Vegapunk/Queen technology.

Brook: Devil fruit awakening. Brook could probably invoke other souls and fire. The Ice he create is from the underworld, so he can probably make its inhabitants and hellfire come.

Jimbei: Probably at his peak (former Warlord and all) but maybe better haki.

Yamato: Devil fruit awakening and maybe better Haki.

Chopper: Devil fruit awakening or better rumble balls from Vegapunk.