Spoilers: Theory for Pandaemonium Story

[Ultimatecalibur]

I know the story is supposed to be original,

The unnamed 6.X Alliance Raid is what is going be original/non-crossover not Pandaemonium.

but I'm predicting we get some FF9 music and references in the bosses like how Eden referenced FF8

FFIX Pandaemonium was an FFII Pandaemonium reference. The FFIX dungeon's theme was even a remix of the FFII dungeon's theme.