From an historical/heritage arms collector's point of view, the .45 ACP couldn't possibly fade away, due to its indelible mark on world history.

It doesn't hurt that the Colt 1911 Government Model was its primary platform for the Allies through two world wars!

Apart from the 2 Argentinian .45s mentioned in an earlier thread, I have a 1911A1 in my gunsafe that was a Korean War battle-field pick-up by my late good mate Don Davie. He removed it from a dead Chinaman after leading his Section on a bayonet-charge into the enemy trenches at Kapyong on 24 April 1951. He brought back a Military Medal, a US Presidential Distinguished Unit Citation, and the Colt.

How could that ever fade away!

On a more contemporary note, all 3 Colt .45s in my custody seem to like a modest charge of W231 under the 230-grainer. In an attempt to replicate military hard-ball for our collector-club shoots, I have been loading Frontier copper-clad bullets that look like FMJ but were much cheaper to run here in Oz. Unfortunately my stash of both powder and projies is dwindling and future supply is uncertain locally.
Hate the thought of messing with a load that has been functioning perfectly!