Saccades are neither random nor very predictable. They are voluntary. You can predict the "salient" parts of an image that humans will prefer to look at, and us

Saccades are neither random nor very predictable. They are voluntary. You can predict the "salient" parts of an image that humans will prefer to look at, and use that information to e.g. improve video compression. But your predictions will always be wrong sometimes because humans are unpredictable. It should be feasible to detect saccades instead of predicting them, and render new pixels more quickly than the eye can move. But it is right at the edge of what's possible, and really needs more reliable eye tracking than is generally available today, along with purpose built rendering techniques and higher resolution + higher field of view displays.