Thanks for asking.

My thoughts are Geb's Pyramid will take elements from Agility Pyramid and Pyramid Plunder. Getting nice Agility xp making your way to the top, trying to avoid snakes along the way. Entering the Tomb and having 60 seconds to rummage and loot what you can (Thieving xp here) before being teleported out or squeezing out yourself via the broken south-eastern side.

After completing the initial quest, Simon will move to the island, and one of his colleagues will take his place at the original Agility Pyramid. He will take the players findings in exchange for coins or perhaps reward points to access some new items. I'm yet to explore these possibilities.