There is so much complexity that needs to be modeled that the fact that these cars need to mimic humans in all conditions gets forgotten sometimes.
Legally, I don't think there's a rule on the books for offering right-of-way via body language. If you misinterpret them and they drive out and hit you, then you would be at fault. Yet, growing up it seemed like an an unwritten rule that, at an otherwise empty rural intersection, if you have right of way, you should offer it up as a kind of generosity to the other driver.
It's a cultural norm that I would dearly miss and would definitely vary from state-to-state and even from urban-to-rural driving inside the same state.
Except for signalling. Hand signals are still permitted, with many jurisdictions still teaching them. Motorcyclists use very casual hand signals, in combination with eye contact. These convey more intention than a sterile blinking light.