I'm pretty sure the main villains are just going to be our group of God's Knights. I don't even think we're getting any more backup.
Because, personally, I still think this is going to end up being a short arc. It's just a gut feeling I have. This could be over in 10 chapters or less.
It really just depends on how long Loki's flashback is. If the flashback is only one or two chapters, I think that guarantees that this is a short arc. If it's longer, like 5 or 6, we might be in for a longer arc. I still don't think it'll be the longest arc ever, but it could be mid-sized.
I don't know. I'm just getting "Jack on Zou" vibes from the God's Knights, personally.
If anything, I think our group of 3 God's Knights could get called back to Mariejois to assist Shamrock in dealing with whatever's going on over there. I could see Gunko getting a call from Shamrock ordering her and everyone else back to Mariejois because he needs backup dealing with the Revolutionaries. Because, Dragon soloing all the God's Knights at once WOULD be kind of neat. Mind, that requires Dragon to actually DO something...which he never has, but there's a first time for everything.
What would be even crazier is if Blackbeard made a alliance with the Revolutionaries to help fight the World Government. Blackbeard and Dragon teaming up. Wouldn't that be a twist? All so that Blackbeard can backstab Dragon, since fighting him might be easier than fighting the entire World Government alone. I don't know, that's unlikely, but it would make for a interesting twist. We do know that Blackbeard is keeping an eye on the Revolution (Chapter 1126). I was originally thinking he'd save the Celestial Dragons to get into their good graces. But, there's no real reason why he couldn't side with the Revolutionaries, instead. It's all the same, as long as it serves his long-term plan.
Between the line about "Not Lingering on Elbaph" and "Speed is the Weapon", I kind of wonder if Oda's leaving himself messages to encourage himself to keep Elbaph fairly quick-paced. I think he wants to hurry through Elbaph so we can get to the ending, already. But, maybe not. Who knows?
As for Loki, I HIGHLY doubt that he's our villain. He's going to end up as our ally, at least. I think a lot like with Momo opening Wano by destroying the walls of Wano, Loki will have to burn Yggdrasil down at the right time, in order to complete the process that will eventually heal the World. I think it's one of the dominoes that have to fall in order to "fix" things. Like I've said before, "destroying the world" is likely a good thing...from a certain point of view.