According to Strategy Page (sorry, no permalinks on SP) the XM29 OIWC rifle program is on hold and in danger of being scrapped. It combined a 5.56mm assault rifle with a 20mm “smart grenade” launcher. Did you ever see Aliens? Pretty much like those rifles. Anyway, it was too heavy, and getting the weight down made it too fragile.
However, the replacement is the XM8. According to Strategy Page
The M-8 is a modular weapon, taking three different barrels for different functions. Most M-8s would look similar to the current M-4, with a shorter barrel than the M-16. There would be a longer barrel for sharpshooters and snipers (longer than the M-16 barrel) and a heavy barrel, of about the same length as the M-16, for the M-8 when used as a light machine-gun. There would also be a “commando” version with an even shorter barrel and no butt stock, for use in tight spaces, and for armored vehicle crews.
If you recall, many US troops wished for a main weapon shorter and more wieldy in urban areas than the M16, but at the same time no one wants to be stuck with only a short-ranged carbine. The M8 could address this by fitting both bill, depending on the expected mission. A 40mm grenade launcher can be added to the M8, but this would eventually be replaced by the M25 25mm “smart grenade” launcher.
The M8 should be available by the end of this year.