Future designs drop the four rails?
Four rail handguards are definitely a part of the AR market, having been used on various models overseas. Kitted out with lights, lasers, and grips, they still seem to fill the ads.
It's not going to be like that in ten years.
All the newer "test" models are dropping rails like dead flies off a bug zapper. What's causing that?
'90's technology optics took up a lot of real estate because of the batteries. And hoisting a couple of lithiums in every accessory added to the weight. One thing that will continue to happen is product improvement and miniaturization. Those accessories will continue to get smaller, use less power, and use it more efficiently. They will simply shrink to the point of being smaller than the mounting system.
They are also being combined into multi use modules, with two or more functions, completely eliminating the need for a second location to mount. The four rails will become redundant, overkill for a newer generation that won't need them. Today's hot ticket item becomes tomorrows retro bling.
It's not quite like tailfins, the rails were used. But the need is becoming much less. The next open competition will be a good example of the change.