I think PG-13 or something like it would come along eventually. Especially now with the ratings system on TV, I just can't the motion picture industry holding out on that front.
But had it not happened for Temple of Doom, I think it was only a matter of time. PG movies were a pretty wide open space.
All the Bond films were PG until the ratings change, Wrath of Khan was PG, Empire Strikes Back and Jaws were PG, but so was Close Encounters. So it was a really wide range and more up to the parent's discretion than it is now. If you're going to a PG movie nowadays, you pretty much know that there's going to be hardly any violence, no languange, and no nudity. That wasn't what you could say back then.