I know this is an old question, but I wanted to pose it again anyway. From what I can tell the Gen4 20 might be coming out next year. It looks like from what I've heard from others that the Gen4 29 will be out before the Gen4 20 is rolled out. I'm wanting a 10mm to go with my Gen3 21SF .45 I'm figuring if Glock can't give a definite release date on the Gen4 20 by this Fall. Maybe I should go with a new Gen3 20SF by then. I know others are waiting like I am. I really like the appearance on the Gen4 21s and want to wait if it's within a 8-10 month time frame on the Gen4 20s.