The ending is not sad, emotional yes of course, there is little of sadness but people is just saying everyone is dead, and the contrary, they are all alive:
All the Dendalions are alive, the Spirits protrct them while they sleep Data world is not destroyed, there was one lifeboat still. Only real one was destroyed, but then rebuilt.
They are just sleeping
Also, the data of everyone is there in the data world, thats why they appear to help Sora in a future
Ephemer on the contrary, he's dead but no, he appears also in the future
I mean, no one is dead (Player's Chirithy is alive as Player's heart still exists) (the Keyblade wielders of real world before KW they can be alive, they have their data in the data Daybreak Town.)
Player is Xehanort, and the heart of the Player is within Xehanort
Or did I not understand? But its not sad, they are all alive
Edited by JOTA