Here's a link to an explanation from an FNH USA Vice President, who basically says the SCAR 16 is dead (for USSOCOM).
Explanation is that early in the program, the requirement was split into two guns, one optimized for 5.56, the other for 7.62. The 5.56 platform was heavier than the typical M4, and as we've all heard before, there are very few advantages to justify a change. The 5.56 was thereofore undesirable, and the project requirement has been changed to return to the original idea, a multi-caliber platform compatible with 7.62x51, 7.62x39(?), and 5.56x45. This means the SCAR-17 will continue on in trials, not the 16.