Oda has been having all the crew either be too reliant on Zoro and Sanji or bring in an outsider to bail the non-ape Straw Hats out.
This is a whole giant demon nightmare creature army we’re dealing with, so no way it will just be Luffy, Zoro, Sanji, and Loki.
I think it will sadly.
If the others can't use Haki, they can't do anything as far as I can see.
It's such a missed opportunity that Robin's flashback in Wano didn't incorporate use of Haki or some training to control it... yet she somehow defeated a Haki user. Robin and Brook are people who should at the very least be competent Haki users, even Franky and this is the bare minimum given their long history of combat.
Usopp and Nami are just sorry to look at, they've become gag at this point and it's a sorry sight.
I think Loki will still be the main villain.
Imu is too big of a villain to fall, more so he's only exerting his strength by proxy of Gunko whom I believe Luffy and co. will defeat.
Once the HK are defeated, I think Loki will fight with Luffy as the main villain.
His goal after-all is to destroy the world and this is just an opportunity.
Sadly, this theme of the lackeys being useless has been a recurring theme for way too long. WCI, Wano, Egghead, now Elbaph. Oda could change it, but the longer he prolongs what should be a basic skill in the New World, the more any powerup related to haki looks like an asspull.