I am pretty sure that if there is another one, Lucas will want to use his haunted castle idea or his chinese religions research. In fact, it would be pretty great if they split that into 2 movies instead of combining them in the same movie, as the Monkey King script did.
If they recycle any ideas from the Monkey King development process, they should certainly nix the intelligent gorillas and the talking monkey, and especially the golden hoop. Indy battling dogs and suits of armor would actually be welcome.
I would love to see Lucas utilize the legendary chinese land of
Mount Penglai (known as Mt. Hōrai in Japan) in one of his Indy stories. There have been expeditions to find it, but it is purely fantastic and could provide at least a good element to the script, even if we never see it.
"There is no pain and no winter; there are rice bowls and wine glasses that never become empty no matter how much people eat or drink from them; and there are magical fruits growing in Penglai that can heal any disease, grant eternal youth, and even raise the dead."