It has been foreshadowed for Usopp(all his lies) and Luffy(his most dangerous ability) , but not for anyone else. It's that particular structure that I don't see happening. On what grounds would Robin be an inspiring leader for the revolutionaries, for example? And who are people like Cavendish under?
I think it's more likely that something similar as Dressrosa happens and everyone follows Usopp. Because that's his thing. He's the one that gives speeches and always tries to get people on his side (usually with lies but I assume it'd be the truth this time).
Everyone else doing the same thing would almost feel like stepping on his turf.
Her entire existence is a ray of hope for the Revolutionary Army, which they literally stated when they met her, and after going through two years, she is also beloved by them, even with high ranking members like Koala and Sabo.
Robin is like the personification of the injustice the WG has shown around the world, and such she is a symbolic figure.
Cavendish can follow Usopp, or Luffy, or Sanji.
Once again, you think of highly epic moments where a leader rallies the people that are supposed to follow them, and then command them.
It´s a much more natural progression of people who feel close to each other and are inspired by a specific person, follow said character.
The Tontattos not because Usopp gives a huge speech, but because he fulfilled their 10 year long plan and did not forsake them, same thing is going to happen with the giants, he already has relationships with Hajrudin, Brogy, Dorry, Oimo and Kashi.
Robin because of what she is and being a Revo herself.
Sanji because he might change the Vinsmokes (i know it sounds shitty since they are pretty much Nazi science elite but Oda went the route of being misguided rather than straight out evil) and relationship with Pudding.
Zoro is obvious, it seems like he might even get a relationship to Wa No in one way or the other.
Chopper because he literally saved them and is regarded as the main savior, and the obvious animal theme they share.
Franky is obvious.
Jinbe is obvious.
Nami is kind of difficult, she had a personal and special relationship with Vivi, but also with Lola. We also do not know if and how the Shandians are gonna be relevant.
Brook has no special relationship so far iirc, might lead a part of Zou due to Hone and also saving them, or something else entirely.