It's heavier than you imagined.This is an interesting development. Like every one else has already said, it would probably include: A Momentary Lapse of Reason, maybe Delicate Sounds of Thunder, The Division Bell, maybe Pulse, and maybe The Endless River.
Maybe outtakes and demos from the studio albums, and maybe the rest of the Big Spliff too, or a bigger chunk of it than has come out as The Endless River. That seems a little bit light for a boxed set...