If there was ever an easter egg to put into the 5th installment, this would be the one.
It would be so meta, it'd probably break the internet.
Just imagine, Old Indy, on a farm, before the action begins, maybe after the first scene. He's out there, in the barn, milking old Jessie, when above him, slightly to his back is a row of hens, doing there thing, when all of the sudden an egg falls from the nest.
Blam, in a flash!
He catches it, sets it on the ground gently, and goes about his business with Jessie.
Then, never go back to referencing it again.
If a scene like that makes it in, the movie (for me) would be a success, no matter what else happens.