This is an interesting development and serves to highlight the historical role of the light machine gun. Most people, including many in the military, have little understanding on what a machine gun is supposed to do. Everyone agrees that a machine gun, including an LMG and automatic rifle, needs to shoot lots of rounds, but outside of that, there's quite a bit of confusion.
Man invented the Machine Gun because it was a great engineering problem, to make the gun automatically load and continuously fire. But after the invention, militaries struggled for years to build up an organization around the technology. Eventually, in the meatgrinder of World War I, they settled on the missions of the machine gun as:
1. In the Defense, to anchor the defensive line, and to build a wall of lead to stop the enemy advance.
2. In the Offense, to isolate the objective (a bunker, foxhole, house) so that the enemy cannot reinforce the target, and to occupy the objective's attention while the rest of the squad/team approaches the objective.
The light machine gun attempts to meet these two missions for the infantry squad, while the medium machine gun does the same for platoons and companies. To keep up with the soldiers on foot, the LMG needs to be small and light enough so that one soldier can carry it and bring it into action, yet still fulfills the above two missions.
The current debate in LMG design is, What are the necessary features to meet the missions?
-Does it require a belt-feed mechanism so we can give it a 200-round belt in a sustained-fire mode, or would the current 30-round magazine be sufficient since machine gun operation usually has enough time to allow a quick magazine change? Can the current 90-round and 100-round drum magazines work as well as the battle-proven belt-feed mechanism? The American BAR served throughout WWII in the LMG role with only a 20-round magazine.
-Does it require a quick change barrel so that the squad can fire thousands of rounds in a defensive engagement against overwhelming odds? Without changing out the barrels in this scenario, the machine gun barrel will melt/deform from the firing stress, rendering the weapon useless.
-Does it need a tripod mount so we can mount it on a Humvee, and to provide accurate, long-distance(600m+), automatic fire from a static position? Or is that a role for medium machine guns and heavy machine guns, but not light machine guns?
These questions are important because modern assault rifles such as the AK47 and M16 provide automatic fire mode to the individual soldier. The soldier no longer has to rely on the squad LMG to be the sole provider of automatic fire. The LMG does not have the overwhelming advantage in automatic fire to offset its disadvantage of weight, size, and logistical and training requirements (as a result of its belt-feed, barrel, and tripod). And without the above three features of belt-feed, quick-change barrel, and tripod mount, the LMG looks suspiciously like any other assault rifles. Witness the RPK and the L86 LSW variant. In fact, the British Army now employs the L86 LSW as a designated marksman rifle, rather than an LMG.
[The Steyer AUG LMG variant is an LMG design that has the quick-change barrel, but no belt-feed nor tripod.]
So armies across the globe continue to grapple with the design of the LMG/Automatic Rifle. The lessons of OIF are now feeding into this debate. In OIF, most of the fighting is done in built-up areas. In such close quarters, the machine guns primarily serve to isolate the objective, firing down alleyways to keep people from entering and leaving. The LMG's length means that it is of limited utility inside houses, going from room to room. The LMG's range is useful as a marksman rifle, but its sustained fire is rarely used due to collateral damage. To the dismounted patrol, then, the LMG extracts a weight penalty for a limited tactical utility.
On the other hand, the LMG was crucial in the early days of OIF phase 4. At the time, units across the country scrambled onto Humvees to maintain security on the lines of communication, and to provide security coverage in the cities. During this mad rush, there was a critical shortage in medium machine guns (M240) and heavy machine guns (M2) to arm the Humvees. The SAWs in the pintle mount bridged the shortage then, and has continued in the role to this day as a vehicle weapon. Therefore, an LMG may be important to the infantry squad not for its dismounted utility, but as a hedge for the days of the Dragoons.
In conclusion, the Light Machine Gun, as it exists today, will probably fade away. In the assault-rifle world, the LMG does not possess enough of an advantage over the assault rifle to continue on as a dedicated platform. Instead, we will see more assault-rifle derivatives such as the Steyer AUG LMG, which shares much in common with the individual rifle. The automatic rifle of the future would ideally have a quick-change barrel and the tripod mount (to get on the pintle). Drum magazines and regular magazines will carry the ammunition for the automatic rifle, enabling the SAW gunner/Automatic Rifleman to share ammo with his squadmates.
Thanks to Noah's Five for Fighting 9/16/08 for the heads up.
Edited for spelling, grammer, and formatting