As new as the Gen4s are, there are a couple of items that bear mentioning already. As the 9mm Glock 17 Gen4s began to log range time, there were some reported cycling malfunctions. It was usually happening with lower powered ammo, common on the range, rather than the full-powered duty ammo used on the street. However, just in case, Glock has redesigned the recoil spring guide rod assembly for the 9mm Gen4s to accommodate the lighter ammo and are swapping out the original part, as needed. All the current 9mm Gen4 17s have the updated recoil spring guide rod, which has 02 stamped on the rear flange of the assembly. The originals do not have any marking. This was not a problem with the Glock 22 Gen4, so no changes have been made to the .40s. In the long run, how many different models are issued in the Gen4 style will depend on the overall demands of the marketplace. The Gen4s are also popular in the civilian market, so look for this trend to continue.
One additional popular feature of the Gen4s is that Glock is providing 3 magazines with each gun. The increase in the price of the Gen4s is largely offset by the value added by the extra mag, so sales have been steady. This brings me to a final word about magazines and the Gen4s. Because the magazine release is reversible, there is an additional cutout on the new Gen4 compatible magazine bodies to accommodate the switch. All Glock magazines, regardless of age, will work in the Gen4s, as long as the magazine release remains on the left side. If you reverse it, you must use the latest version of the Glock magazines. This is important from an agency standpoint, because earlier magazines could still be in department inventories and they should not be accidentally issued to any Gen4 lefties who may be out there. Over time, this will resolve itself, but if you are a left-handed shooter with a Gen4, make sure you have the latest magazines.
As always, the market drives the design changes, so there may well be other projects and changes in the works at Glock. For the past 20 years there have been rumors of a rifle or carbine, but so far nothing has happened. I mention that now because I heard just recently that Glock is finally going to make a move on this. Is it true this time? You certainly didn't hear it here first, but maybe, in spite of global warming, the temperature in the nether world may be finally starting to drop.