Around 1905, when a Mormon from Utah was playing around with guns in Belgium, the only way known to make a small auto pistol was to make it for a smaller cartridge. .22 LR would seem a good choice, but the bullets weren't crimped, and .22 Long was not very powerful. Plus both were rimmed cartridges. So the guy from Utah, whose name was John, pulled his usual trick with a semi-rimmed center fire case, and came up with the 6.35mm Browning, which, by some coincidence, was his last name.
Later, when he brought the idea back to the U.S., and let Colt make some guns for that cartridge, they called it the .25 Automatic Colt Pistol cartridge.
But fast forward a hundred years, and other designers got into the act, using new ideas and new materials, and they managed to turn out pistols in .32 ACP, and .380 ACP that weren't much bigger than the guns Colt made in .25 ACP. Even the 9mm Parabellum, which in Browning's day was strictly for big guns like the Luger pistol, now have a home in pistols of pocket size or smaller.
So is there a place for a new pistol in .25 ACP? Somewhat sadly, I have to say there is not. There are plenty of the small guns around, and unless the gun ban gang has its way they will be around for many, many years. But I doubt there will be any new .25 ACP pistols from here on.
Jim