The big problem, for those not reloading, is that while "alternate" calibers, meaning those rounds that are less popular, not service rounds, and including those that are semi-obsolete is, that while they may be the last thing you find on the shelf, they are also the last thing replaced.
In general (and in "normal" times) the way the ammo manufacturers work is a combination of regular production (those rounds in high volume use) and "seasonal" production, which is those rounds with low demand that are only made once in a while.
Now, seasonal doesn't mean every fall or at Christmas it means every few years, based on usual demand. When the warehouse stock level reaches a previously set "low" quantity, the factory tools up a production line and cranks out the seasonal round until their stock is back up to "full" then shuts it down, packs away the tooling and that line goes back to making the regular production rounds.
How much of what they make as seasonal ammo depends on previous year(s) demand, and when something spikes interest in a formerly "moribund" round, such as use by a popular tv/movie character, existing supply can be gobbled up and a "shortage" results. We've seen this over and over in previous tmes, mostly with rifle rounds before there was any "election panic" or virus panic complicating the issue.
We see it most with the "obsolete" rifle rounds, because there are more of them, many go back to the black powder era, but there are also fairly recent ones that were not popular enough to stay in production. .
But it happens with pistol rounds too. Also happens with gun supply. WHY do you think there are price surges and scarcity with various gun models, especially discontinued ones? Because for years some barely sold enough to stay in production, or not enough to stay in production, then some movie star uses one in a hit film and then everyone has to have one.
One of the biggest and most famous examples of this is the S&W .44 Magnum. Since the late 50s they sold, in small numbers, steady enough, but nothing huge. Then in 1971, Clint Eastwood's Dirty Harry used it and made it "THE GUN" to have, and demand literally exploded overnight. By the mid 70s, the factory was still running more than 2 years backordered, and people were paying double MSRP just to get one in their hands, today.
The same applies to old calibers, when something puts them "back on the map". War anniversaries or a round hitting its centennial do this sometimes.
.45 Colt and .45-70 were still poking along sales wise, after production resumed following WWII, not a lot sold, but enough to keep them going, until 1973, when they turned 100 years old and got a lot of write ups about them, increasing interest and demand, back to or even exceeding their historical levels and continuing to this day.
The "feast or famine" cycle in ammo is the normal pattern with low popularity rounds. Today with the virtual feeding frenzy for any ammo in any caliber isn't going to change that. what it is going to do is extend the lean times , exponentially.