updated 10:33 am EDT, Tue July 8, 2014
Unlikely to be implemented in near future
The US Patent and Trademark Office has granted an Apple patent on a technique for fusing together all-glass housings for portable electronics, and even larger devices such as monitors and TVs. Apple notes that glass can actually be a heavy material, especially if it's layered to defend against damage. The patented fusing concept would allow Apple to cut down on weight by shifting the burden to strategic points of structural integrity, instead of bulking up the glass in general.
Apple also suggests some cosmetic touches. These might include tinting the back of a device to hide internal parts, or "roughening" planar glass to scatter and diffuse light around the borders of a display.
The technology is unlikely to make it into any products shipping in the near future. Glass, even Corning's Gorilla Glass, is currently too prone to breakage to make it useful for protecting every surface of a device. Apple has even been shifting away from glass, reducing the amount used in the iPhone 5s; the iPhone 6's back may be entirely metal. Sapphire could be a solution, but Apple is only now beginning to use the material for displays, much less the entire body of a product.