I am not a papyrologist or a classicist, rather I'm a computer scientist, so my expertise is unfortunately not in _what_ the scrolls say, rather how we get there. That being said I think and hope that there will be a trove of things that has no known provenance at all, completely lost works that elude the public memory.

Aristotle's second book of Poetics, of course.

Here's a list. The scrolls are from a library that burned in 79 AD.

https://en.wikipedia.org/wiki/List_of_lost_literary_works

Probably a lot more texts of Epicurean philosophy and not a whole lot else unfortunately according to my papyrologist friend.