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.