I can't imagine that this will be a big seller. The casual fan has probably already bought one of the other collections out there, so no need to get this one.
Some hardcore fans will buy it because of the new songs or out of completists reasons, but I think a lot will give it a pass. I would like to hear the new songs, and probably they will be up on spotify, but I'm not giving away money for a full priced cd for songs that I already have, sometimes on multiple records.
Couldn't they just tour for the 40th anniversary and then release a new album with all new songs?
Or maybe relase the remastered back catalogue with bonus tracks? That would be more interesting than a greatest hits compilation, but still I wouldn't probably buy it.
Or release some live material from the earlier years, surely there must be something in the vaults?