Yeah Elbaf is definitely not going to be a short arc like some people think.
Kid and his crew will be involved during that arc, if those spoilers I saw are true then it looks like Bege and his crew will also play a role during Elbaf as well.
Urouge will most likely play a role, if Bonney doesn't separate from the SHs then she might join them to Elbaf.
If Big Mom is alive then there is a good chance that she and her crew will also be involved and if not Big Mom herself, then maybe just her crew.
Elbaf is pretty much being setup as the next Dressrosa/WCI/Wano, the Elbaf arc will probably be more than 50 chapters.
To me it feels like all of this is leading to Fullalead with Egghead being our Punk Hazard (intro arc) and Elbaf being our DR/WCI (middle arc) and Fullalead being Wano (climax arc) essentially.
Kid had the 2nd longest pick from Wano, meaning Elbaf should be next or at least before Fullalead if thats where Law was going. Elbaf could focus mainly on giant/sky/moon lore, eventually culminating into one big incident with Blackbeard at Fullalead potentially.
Plus, it almost makes sense Fullalead is "Final" island before Lodestar. If you think about it, many great pirates probably reached Lodestar and learned about the RPs, but were left at a standstill at that point. That would mean you have tons of pirates just unable to do anything else, so they converge at Fullalead.
You also have people like Jean Ango (the bounty hunter from DR) mentioning that all of the Level 6 inmates from Impel Down all went somewhere, which could suggest this island too.