Hard edged, per-pixel light blocking is impossible for the foreseeable future. What's possible today, and what Magic Leap has, is diffuse dimming of large areas of the display.

The problem with light blocking is that when the blocker is millimeters from your eye it is completely out of focus. Unlike for the display, you can't use optics to make it appear farther away and in focus because the direction of the light it needs to attenuate can't be modified (or else your view of the world through the glasses would be warped).

For a near-eye light blocker to work, it would need to be a true holographic element which can selectively block incoming light based not just on its position but also its direction. Each pixel would essentially be an independent display unto itself that selectively blocks or passes incoming light based on its direction, instead of indiscriminately like a normal LCD. I have no idea how such a thing could ever be fabricated.