I'm honestly really surprised to see so many people all over the net talking about Elbaf.
I've got to be honest, I've 100% written it off.
We've got so many loose ends to tie up in the (ever rolling) 5 years of One Piece we have left. World Government, Akainu and the admirals, Im, Revolutionaries, the Reverie, Uranus, Shanks and Blackbeard, the Underground, Vegapunk, what did Doflamingo have over the Celestial Dragons, the destruction of Fish-Man Island and the purpose of the Ark, several Worst Generation pirates that have had fuck-all screentime, what's the deal with Edward Weevil, Zoro beating Mihawk, and then a whole host of other stuff that I can only assume will be dealt with on Laughtale (Void Century, Will of D, Joyboy, the One Piece, etc).
The time where we bounced from fantastic location to fantastic location is long behind us. We've been plot railroaded ever since Punk Hazard. Wano is the culmination of 8 years worth of plot and I cannot believe that we'll be going to Elbaf next just because it's a place Usopp said he'd like to visit 20 years ago. Locations in One Piece are much more heavily foreshadowed than that now and wherever we go next, we'll A. know it before Wano is over and B. I would bet anything will be World Government related. Mariejois would be especially apt as half the stuff I mentioned is there, but New Marineford wouldn't surprise me either. If the Road Poneglyph ended up on Mariejois, that would be geographically close to Fish-Man Island, meaning that it's a believable place for it to have ended up and we can deal with Fish-Man Island loose ends while dealing with World Government loose ends that are all conveniently in one spot right now.
So what exactly is the point of going to Elbaf?
Usopp is the only Strawhat to have already achieved his original goal (become a great warrior). You don't see anyone chomping at the bit to find the All Blue or entertaining any notion that we're gonna map all the seas in the world, but we have to go to Elbaf to make Usopp a warrior when he already is a damn fine one?
Now everyone is saying that each East Blue Strawhat needs their own arc, which is a really good theory if it pans out for Zoro (though Wano sure is taking its sweet time on that end). Because not only did Sanji get an arc recently, Usopp already had a major arc where he became a deity. Hajrudin has already pledged the giants to serve God Usopp, so what could possibly happen on Elbaf but "Hi, nice country, oh you have the Fish-Man Island Road Poneglyph for some reason, that's cool, bye!"
To be frank, Island with big people is hardly even creative enough for One Piece anymore. Wanting to see a place just because it was name dropped a long time ago didn't work out so well for Fish-Man Island.
So while I'm sure that at one point in time there was a One Piece draft that involved a stop at Elbaf, I just don't see it unless One Piece drags on for 10 more years. I wouldn't eat my hat over it, but it just doesn't make nearly enough sense that everyone would be in agreement. If One Piece is really to end soonish, then I'd bet it's Mariejois->Laughtale. If he's full of shit and he might be, then I still wouldn't give Elbaf even a 50% chance as I think it's narratively dead.