There's always an opportunity for improvement. Maybe the first autonomous sensor suite can see as much as humans can. But there's a case to be made that we've got a pretty limited view. Sensors that have better light sensitivity could improve on our vision. Being able to improve on seeing through dense fog or snow would also help. Analyzing the roadway for upcoming ice, nails, etc.Once you have full autonomy then there's not really a need for better sensors or faster processing.
Full autonomy can mean "drive like a human" but it can also mean "drive a hell of a lot better than a human." I think we're shooting for the latter, and that's a moving target.