Shortly before Indy 4 hit theaters, Spielberg was preparing a film set eleven years later, in 1968. From Wikipedia:
The script to my knowledge has never leaked and the project continues to be kicked around. If it's ever made it may show traces of Spielberg's influence (for instance, the arch enemy in American Sniper). His own interests during that era:The WGA strike, which started in November 2007 and lasted 100 days, delayed filming and the project was suspended. Aaron Sorkin was later to continue to rewrite the script for Spielberg, and the director intended to mostly cast unknowns to keep the budget down.
"Staying out of Vietnam and getting my grades to a point where I could retain my student deferment, which is what all students coveted during the Vietnam War. That was also around the time I was sweating out the draft lottery. I had a high number. I was lucky. My immediate political activity was based on self-preservation. I had a draft counselor. I legally did what I could to not go. But if I had to go, I would have gone. That's the truth."