I know of a few agencies here in New Jersey that currently carry this round. I believe a few federal agencies including the United States Secret Service and Air Marshalls use this round. I have also read that multiple state police agencies and highway patrols use this round including Delaware, Rhode Island, Virginia, Montana, and North Caroline. As long as the federal government, state, and local law enforcement agencies continue to use it, it will still be around. Supply and demand, plain and simple.
If you are worried, do what alex suggested and buy a 40 that you can swap barrels with. I have a sig p226 and It is simple to switch the 40 barrel/slide out with a .357. It even takes the same mags (they are stamped as both)