I mentioned it before in some comment, but I suppose it doesn't hurt to write a quick note as a blog psot as well:
Aviation enthusiasts keep reviving the idea of a return of the glider for cargo and airborne troops delivery. It's a cheap means of adding cargo capacity, allows for some stand-off on part of the pricey transport aircraft and it's kind of silent.
Well, it won't happen - because it already happened almost two decades ago.
The old gliders won't return, but the gliding approach has long since been revived with HAHO parachuting*, robotic cargo glide parachutes and even prototypes of robotic cargo tailless gliders. There is simply no need for the steel frame, wood and fabric construction of old any more.
A few links to examples I found in a very quick, very lazy search trying to rediscover what I remembered:
Very low altitude drops (500 ft) are also an old hat; wartime drops of small teams were even done at 150-200 ft as early as during the Vietnam War.
There's really next to nothing to be gained by a comeback of the early military gliders. To discuss a possible comeback may be entertaining to aviation enthusiasts, but it's pointless.
*: There are even electronics-laden helmets to help HAHO parachutists to navigate to the landing zone over dozens of kilometres at night..