> One approach that has been discussed recently is to create a pointcloud using stereo cameras (similar to how our eyes use parallax to judge distance). So far this hasn’t proved to be a great alternative since you would need unrealistically high-resolution cameras to measure objects at any significant distance.

Doing some very rough math, assuming a pair of 4K cameras with 50 degree FOV on opposite sides of the vehicle (for maximum stereo separation) and assuming you could perfectly align the pixels from both cameras, it seems you could theoretically measure depth with a precision of +/-75 cm for an object 70 meters away (a typical braking distance at highway speeds.) In practice, I imagine most of the difficulty is in matching up the pixels from both cameras precisely enough.