You'll know it when you see it
Why? Does the mummy have a penis?
it means that the previous Mummys are possibly in this universe making this The Mummy 4
I saw it. The book, right?
the book of the dead
I'm not sure that's meant to be a call back to the '99 film. The Book of the Dead is a real book and quite well-known. It makes sense it would find its way into a story about ancient Egypt and the supernatural.