Why not?
1 unreleased demo is considered like a new song..
The Cast in Steel album included 1 80's demo..
Which 80's demo?
She's humming a tune was written in the 80's, but the demos are from foot of the mountain.
80's Demos on the forthcoming album would make no sence.
Don't get me wrong, i love the demos from the 80's and a song, written in the 80's would always be welcome.