Sgt. Pepper - you are so right; .40S&W is an awesome caliber, especially for reloaders, where you can tailor a great range of loads for different purposes. And .40S&W is exceptionally wide-spread in terms of various pistol offerings, something which is, unfortunately, not true of 10mm.
Not long ago people were crowing that 10mm was dying (not that it was ever very widely used). But today, it is increasing in presence.
In spite of the large spike in sales of pocket pistols and 9mm (driven by the huge increase in citizen concealed carry), .40S&W will remain a widely-used, common, and mainstream defense caliber for many, many years to come.
Sales of .45auto and .40S&W pistols and ammunition will not be as high as 9mm, but these three will remain the most common and mainstream of pistol calibers, by far.
Agencies trade in their pistols regularly and have done so, regardless of caliber, for many years. They will continue to do so. Many agencies will go to 9mm to lower their ammunition costs and dumb-down to the lowest common denominator of shooter capability, but .40S&W isn't going away by any means.
I doubt that very many here on the forum have bought or fired .38 special, .357 magnum, or .44 magnum in a long time, if ever! Yet, those calibers are still extremely readily available and will continue to be. .40S&W is dramatically more popular and common than .38 special or .357 magnum.