Wow, this IS an old thread. I still LOVE this type of conspiracy though. I'm most interested in handgun cartridges. Why? Because when a handgun cartridge DOES become obsolete, all of the guns chambered for that cartridge eventually go up for sale to the public as "police buybacks", and that's one of the most American things ever.
My thoughts:
.45 GAP
could stay around if Glock wants it to. The company may be stubborn, but assuming they stay up-to-date with PD demands and needs, which is likely considering PDs are born and raised on Glocks these days, the cartridge should be fine. One has to acknowledge that LEOs come in all different sizes (*cough* cause they have to) and it already has PD contracts. If Glock was by chance getting cuts on .45 GAP ammo sales, they'd be golden.
The .357 Sig will stay. The numbers really look best with 115gr. bullets, but those numbers look
really good. Of course, "the numbers" are the only thing to look at if you don't already own a gun chambered for this round. Brass is made easily from the already accepted and available .40 S&W and there are so many 9mm/.357 bullets that you can't go anywhere without tripping over them. The .357 Sig also has potential for the types of folks who like to "hot-rod" pistols, which is to say, the guys that like 10mm but not the recoil. As a matter of fact, I'm suprised I haven't seen a 5" 1911 chambered for this round for competition. True, .38 Super probably makes more sense.
Of interest to me are the bottlenecked rimless cartridges (.357 Sig, .38 NAA, .32 NAA), and smaller-caliber rimmed cartridges (.327 Mag). You're more likely to get a CNS hit with penetration than with expansion, and all of these cartridges serve that purpose, as well as putting more ft/lbs. of energy in the gun to begin with.
With concealed carry increasing in popularity daily, I think handgun cartridges will see a bigger
percentage of increase in cartridge options than rifles. I emphasized percentage because folks will always be more interested in tinkering with rifle cartridges than with handgun cartridges, but relatively, I think handgun cartridges will see a considerable focus.