The Firearm Blog reports that Polish gun magazine MilMag reported this news. Apparently, the requirements are,
Either in 5.56x45mm or 7.62x51mm caliber
Ambidestrous controls
Standard NATO rails
Two barrel lengths
No heavier than 3.6kg
15,000 barrel life, 30,000 firearm life
The speculation started when H&K 433 hit the news. Supposedly, the two contenders are H&K 433 and Steyr-Rheinmetall RS 556
The submissions are to be submitted by May 22, 2017. Selection will be in 2018, with production to run from April 1, 2019 to March 31, 2026. The budget is 245 million Euros.
From: The Firearm Blog