The .45ACP crowd has been aging for quite some time. There will always be those who appreciate a good 1911 in .45ACP, especially since the platform and chambering are so closely associated. However, the selection of non-1911 .45s have been long dwindling.
Heck, I'm a fan, but have far more 9mms and even .40S&Ws than .45s (actually, I have the same number of working .40S&Ws, three of each, with one non-functional .40 that I need to send to Taurus to get fixed, I've only been putting it off for about 10 years). I'm probably going to trade my Officer and Commander sized 1911s (a RIA and S&W respectively) on one steel framed full-sized 1911, and I will probably trade my .45ACP home defense gun (a DAO SIG P250) on another .45ACP auto for home defense, so soon the difference will be greater. Most of what I buy and shoot are 9mm, and most of my ammo purchases are in 9mm (I only keep a few boxes of .45 on hand and only buy more when I use it, I stock a little .40 and a fair amount of 9mm at any given time, and I buy both in bulk once in a while).
Given modern bullet designs, I'd rather have 15-17 rounds of 9mm or 12-15 rounds of .40 vs. 8-10 rounds of .45 in the same sized package.