Harrison Ford has been ready for a new Indiana Jones movie since his interview about Cowboys and Aliens in 2011. It is Steven Spielberg that is holding things up. Spielberg likes to delay movies. The same for J.J. Abrams.
Spielberg doesn't understand that being in your 70's poses health issues and a weaker immune system. Loss of energy. A heart attack, a stroke and dying of natural causes in your sleep can happen.
Spielberg will be 71 this December. Harrison Ford is already 75.
They should have made more Indy films in the 1990's.
For some reason, Spielberg wants Harrison to be so old to play Indy again and I don't think the film will be as enjoyable. Maybe Spielberg has some jealousy there for Harrison's vim and vigor.
It is not easy for a man to be so physical and strong in your 70's. Spielberg does not know this. Spielberg doesn't look like he lift weights and does push ups himself. Spielberg can just sit in a chair with his one kidney.
Of course, Harrison has been wanting to do this fifth movie as soon as possible. It may be his swan song.
Steven Spielberg knows darn well there will not be any more Indiana Jones movies after 2020 with Harrison, like he says there will be.
As far as trying to find an artifact for the movie...The Librarian tv series (TNT) comes up with artifacts every week the cast is in search for or trying to rescue from a villain.
An artifact that has a biblical connection like the Ark of the Covenant and Jesus' cup was my favorite.