M9 is a piece of junk. I expect the M&P to replace it. No way they will pick Sig or Glock for political reasons.
The industry insider called the Sig a “workhorse,” but said the P229 is an unlikely selection because it is double-action only and has no positive safety.
I would say Glock, but the lack of an external saftery knocks them out of the race unless they are developing something I don't know about yet. The M&P have the availability to come with a manual safety and they are good guns. The FNP series also can have manual decocker/safety. I can't see them switching from the 9mm. Be a lot nicer if they could carry +P hollow points. And from what I understand the M9 can't fire +P's because of the open slide design?
I have seen multiple reports about the military wanting to retire both the M9 and M4/M16 over the last couple years and still have not seen any progress.
I might be wrong about this, but it seems like I remember reading that NATO spec 9mm is loaded to +P levels.