Don't most of them already collect that info? I know it prompts me when I make a reservation on US Airways' website to verify the TSA Secure Flight info, and it includes a redress # and known traveler # already. They'll have to set it up to print or not print the barcode, but I can't see them holding this back, especially since it's a great perk the airlines can offer their elites (you don't need Global Entry to get into the TSA system, just that if you are in GE you are also automatically in the TSA program now as well, plus NEXUS & SENTRI inbound).