Are we talking realistically here? Or if we were calling the shots? Because those are very different things.
Realistically, the M9 and 9mm are going nowhere. They'll keep on issuing ball-ammo, terminal performance will continue to be marginal, and sidearms will continue being unimportant.
If I were in charge, one of two things would happen.
1) We'd keep the M9 and start issuing HP ammo with steel penetrators. They'd expand in tissue but penetrate some armor. I don't care what the international conventions say.
2) We'd do trials on 45ACP pistols and keep ball ammo. I think it's unlikely the 1911 would win again, despite its merits.
I don't have a 45, but if I had to use ball ammo, that's what I'd want. If modern bullet designs were available, the reason to use the large round is less, and additional capabilities might be added.