I think so too.
I'd hazard we've seen all of the shadows in action already, I don't see Oda bringing a new character into the mix before the fights end, but there will be a clear mention that "these" are the Nine Shadows.
And it doesn't have to be an actual attack, the prophecy is that they will save Wano, not that they will all deliver the final blow to Kaidou at the same time, and right now Kaidou is not only a dude fighting but also floating island about to land on the capital, and don't forget Orochi is also a part of the tirany that holds Wano.
The big final scene of the fight will include Kaidou down, Orochi down, and Onigashima landing safely, with nine characters standing tall above it.
Then, we party!!
Btw, i've been thinking and since Wano is closed off from the world these nine shadows can actually be that. Shadows and symbols and not focused on actual individuals.
So the shadow isn't Luffy, it's his Gear 4 bound mode, which resembles a guardian deity, replacing Hyogoro's young self, who also looked like one.
Luffy is a type of Nio guardian deity, Momo is a dragon, Yamato is a guardian wolf, Marco is a phoenix, Zoro is a Samurai, and that's 5…
Anyone else wanna chime in on this theory? I can see Law and Kidd being part of it, maybe even Killer, since they were all on the rooftop, but not what archtype they could hold. Tama as a beast master? Hey, Japan invented Pokemon, beast masters are a national symbol for them.