I like the "pagan" artifacts from long gone civilizations... but it seems to me that it was the Bible artifacts that did the best... the Ark... the grail...
What if they did something in the future along the lines of... Moses' staff... The Sword of David... The Ten Commandments... or whatever...
And as for Harrison... all he needs to do is keep in shape... and exercise...
Spielberg is booked for the rest of this year with The Trial of the Chicago 7... as well as 2009 with Tintin, Lincoln (which I will definatly see) and Interstellar...
I say at the very beginning of 2010 they begin shooting for Indiana Jones V... Harrison will be 67... Not too much older than 65... Do one final movie with Harrison as the main character... this time hunting a Biblical artifact... like... the Ark! (Noah's...
)... Set up Mutt's own future adventures and him taking the mantle of his father... maybe have Indy give Mutt his hat as a gift before retiring.
Indiana Jones VI (or rather "Mutt Jones") is about Mutt Jones' adventures... at the very beginning of the film he still dresses in a motorcycle jacket and regular shirt and pants (but he does where the fedora)... Mutt goes on some great adventure taking his dad (Indy being the 2nd Main Character) along with him (Last Crusade type thing). By the middle of the film Mutt has accepted the entire outfit... have Mutt borrow his dad's whip during the adventure. With Mutt's Adventures it's a good opportunity to introduce some new, young, leading lovers (which Indy IV lacks, and Indy V will probably lack). May I recommend Natalie Portman?
Have Mutt's adventure be based around King Arthur's Sword or something...