IMO the 9mm standard won't change.
. 45 ACP is a poor choice here, 9mm is better, but 40, 357 Sig, or 10mm are even better options.
There is no scientific data that backs up that suggestion. Plus the recoil of a 10mm in a Glock (as suggested) is a much less manageable platform than an M9. Why? Physics. Reliability of the Glock itself (all calibers) seems feasible, just not in 10mm as far as the role it needs to fill. Just think about it...Accuracy is number one. Some can argue all they want but if you cant get good shots the threat will remain alive for sure. Now if so many people are not as efficient with the 40 as the 45 or 9mm because of recoil and are moving away, why in the world would we think the 10mm is any more manageable or feasible for a combat pistol?
NATO: Yes we have broken from using the NATO round before with the 45acp but it makes since not to. I know we have not had problems with Logistics and ammo supplies because of breaking from the NATO round but that is us and it doesn't make since to assume it won't happen. I don't see our military doing it again either. Not because we follow NATO either. Reason: Until there is some scientific evidence that a different caliber is much more effective for the role the 9mm Makes since. Maybe some have not had that epiphany and maybe never will. But more 9mm rounds can be put into a magazine than 40, 45, 357sig, or 10mm. Plus they are lighter which is important for anyone who has to pack weight around all day.
We have had caliber wars before but there are more reasons to use a standardized round that is effective in the given role. You may have a different view or preference personally but this decision is on a larger scale. There are more factors involved. I can't say it won't change. I can only say it makes since not to change it until it is proven that there is a reason that it needs changing and I don't see that.
Me personally?
I like the 40 for better small barrier penetration (light doors, drywall, car door windows). Not much better but the difference could mean a lot if I ever encountered it. Maybe the 40 plays a better role because of that and the increased recoil may not make a big difference to the guy carrying it in combat. Could be a more effective round. Yet the 9mm has not been proven ineffective in it's roll yet and therefore it's not broken. Even better yet if it does the fix to change to a different caliber could be inexpensive and the platform/design chosen may to have that option before accepting.
Look at the .223/556 round. More can be carried and they kept it. It's effectiveness has been the subject of debate and they did not change it. However the effectiveness of the 9mm and it's role has not. Other than FBI requiring a caliber change due to their perception of effectiveness (now returning to 9mm) and the military doing away with .38's, movement has been toward the 9mm standard. I see no reason they will change the caliber now.