Ven/Vanitas didn't share the same body back in bbs. But thats the entire point. Vanitas is defeated and Ven's heart is healing inside of Sora's. For Vantias to be back this is a past version of Vantias that is time traveling. Vantias is the darkness inside Ven ripped out and personified but current day Vens heart is no longer shattered. Ven won that fight. So how the hell is Vantias existing?
Also terranort was shown in the new trailer. Which is another wtf. Baldynort is back. So why and how is Terra still fused??? I'm betting this is a flashback
Riku replica has already been shown in his dark suit with his normal hair and eyes
This new Riku has silver hair noted eyes and the org coat. It's clear it's 2 different rikus. I'm not saying it can't be data Riku but it just makes sense that it's kh1 Riku. If it is this finally answers the question on how the hell Riku magically went from soul eater to wttd. Now the Only other question that's still unanswered from kh2 is how did Riku get kairis keyblade
And before u ask how can kh1 Riku and current Riku co exist. Young xehanort and baldynort is already doing it.