The XM17 Modular Handgun System competition is over and the winner declared. The winning entry is SIG's P320 pistol. The P320 represents a new design trend in firearms, where the serialized part (and hence the actual firearm for legal purposes) is a removable steel skeleton. The steel skeleton provides the strength and rigidity for the pistol's frame, and contains all the fire control parts.
That means everything else -- the frame, the slide, the barrel -- can be swapped for off the shelf parts that require no special purchasing regulations. The benefits of such a system are pretty significant. You can purchase a full size P320, then buy the compact frame and effectively have two pistols. Just put the steel skeleton into the one you want to use. Likewise, you can buy a whole new slide and barrel including in completely different calibers.
I've never fired or even handled a P320, but they seem to be very well regarded. I can see why the design would be appealing to the military from a logistics and cost perspective. With traditional pistols like the M9, if the metal frame is damaged then that is effectively an entire unit lost to usage. With the new M17, the steel skeleton would just be swapped into a replacement frame and the damaged one discarded.
The procurement includes options for other branches of the Armed Services to also acquire the M17, so this may become widespread beyond just the Army. Though interestingly enough, the Army Rangers, Navy SEALs, and Marine MARSOC have all recently adopted the Glock 19 so it remains to be seen how widespread the M17 will be.! No longer available