The only music we can use is the stuff in EaW already, and our own creations. Ahdanack did a bunch of stuff for the Empire of the Hand (Battle, ambient and galactic, as well as the menu theme) but hasn't done anything since, so if/when eotH is playable, that's the only original stuff you'll be hearing unless Ahd starts doing more work or we get a different composer.
Other than that, the New Republic and Remnant will be using the Rebel and Imperial music from EaW respectively.