At NRA 2014, Glock confirmed that they will be offering factory threaded barrels for Gen 3 firearms later this year. Included models will be the G17, G19, G21, and G23. Interestingly the full-size .40 G22 will not be included. Per the representative present, the G22 will not be included as “.40 does not supress well”. (I agree, as I shoot G22’s). The G23 will get the barrel to make it Canadian-legal.
Threaded barrels will be available in complete firearms and as stand-alone options this summer. Glock estimates around June. As a bonus, the long-slide G17L will also be produced in the same timeframe.
No Gen4 Glock’s are slated for the factory threaded barrels in the short-term. If demand is there, Glock may produce them for Gen 4 pistols, likely the same models barring the G23 in the US.
I also asked about a single-stack 9mm. The representative was suitable evasive: “Who knows what we will have for upcoming products?”