With all the early copies of the 1.5 collection and the hardcore gamers that have already beaten them, something has been revealed. During the end credits of the Kingdom Hearts 1.5 HD ReMix, scenes from Kingdom Hearts 2, Coded, and Birth by Sleep can be seen. 2Ch and FF-Reunion users are among those who described these 3 games in the end credits of the collection. More information to follow...
Credit to Libregkd for the news update
Update: The scenes can be seen in the credits of Leta_jp's livestream here.
The credits roll from 6:50:00 - 6:53:45
Kingdom Hearts 2 scenes (6:50:00 - 6:51:52)
Kingdom Hearts Re:Coded scenes (6:51:53 - 6:52:18)
Kingdom Hearts Birth By Sleep scenes (6:52:19 - 6:53:18)