I didn't see this posted elsewhere after a short search, so here goes:
“Kingdom Hearts III and Kingdom Hearts 3D are not the same. However, it is a brand-new adventure starring Sora and Riku. The story is on par with that of a numbered title, and I’m sure the ending will shock fans.”
Nomura also stated that the ending in Kingdom Hearts Re:coded relates to 3D:
“There is a hint regarding Kingdom Hearts 3D in the secret movie [of Re:coded]. Players will find out once they see for themselves, but the movie includes some shocking statements and dialogue that pertains to Kingdom Hearts 3D, so it’s definitely worth watching!”
link
“Kingdom Hearts III and Kingdom Hearts 3D are not the same. However, it is a brand-new adventure starring Sora and Riku. The story is on par with that of a numbered title, and I’m sure the ending will shock fans.”
Nomura also stated that the ending in Kingdom Hearts Re:coded relates to 3D:
“There is a hint regarding Kingdom Hearts 3D in the secret movie [of Re:coded]. Players will find out once they see for themselves, but the movie includes some shocking statements and dialogue that pertains to Kingdom Hearts 3D, so it’s definitely worth watching!”
link