It will have 15 rd mags. There were complaints about the Winchester WWB ammo causing jams. I believe the new mags are a little longer to allow for longer length reloaded ammo. Something to that effect, but don't quote me on it.
I wouldn't be surprised if regardless of all that is said, if the only noticeable difference will be the FNP to FNX name change.
I pray every night for the Remington ACR to be brought to the civilian market sooner than later.