If Sora and Kairi do end up seeing hallucinations of their respective Nobodies (possibly more than just Roxas in Sora's case), how do you think they will play out? I'll go first.
Forced flashbacks. For example, Kairi seeing Namine's first memory of her creation.
Reflections turning into Roxas, Xion, Ventus, Namine, and/or possibly Vanitas. KH3D had me thinking that he'll come back. Just imagine, Sora being in front of that small waterfall in Twilight Town. His own reflection turning into Roxas.
If Sora and Kairi do end up seeing hallucinations of their respective Nobodies (possibly more than just Roxas in Sora's case), how do you think they will play out? I'll go first.