It appears that the Rivers of Light soundtrack has been made available online. Follow the link and proceed at your own risk, as this is not a site that we’re familiar with. After a quick listen to a few tracks, we can say that this does sound like the music played at the preview we attended.
UPDATE: Someone has uploaded the entire soundtrack to YouTube. Original link below.
http://www.yz-zr.com/album/9c94Bqeba81
UPDATE 2: It looks like the original release date was to be December 2, 2016 according to UK music site HMV.
Also, Spotify has a placeholder up for the album, but no word on a release date.
Here is the highest resolution image of the album art I could find.
H/T: rteetz