I think there are a good bit of songs that are at a completed stage like NRL with Chester's vocals, but that is one song that is incredibly unlikely to be released. There are fans that don't know that song, so why would it make sense to release a demo of it?
The most likely reason that this was a mostly instrumental album was because we got THP just a few months before LPUXIV. Next year should have more songs with vocals because we will most likely not have a major release from the band.