Nothing like predicting the future to pass the time. But it is instructive to look at the advertisements in old gun magazines, say around 1960, for comparison.
Yes, the prices were low but so were the new guns. But there were some really good things to be had, if you could scrape up the cash, things that are pretty scarce on the ground these days. Things like Lugers, 1911 pistols, 1917 revolvers and lots of the oddball automatics from Europe. There never seemed to be any Japanese guns. Mausers didn't seem to be at all common in the advertisements except for Swedish Mausers or South American variations. You also never saw Mosin-Nagants, Swiss army rifles, M1s, and next to none post-war surplus. Lots of Lee-Enfields, however, and Webleys, and deactivated machine guns. The last deactivated machine gun I saw was a Madsen.
Most of those are pretty scarce any more, relatively speaking, though you certainly will see them. New lots of Mausers seem to turn up with some frequency since so many countries used them. In fact, in 1960, lots of countries still had bolt action rifles in active service. For that matter, we were still using M1 rifles and BARs in the 1970s.
The future doesn't look so rosy since just about everyone that has an army uses some form of automatic rifle or something that otherwise will be disallowed, not that that has stopped this country from being flooded with all manner of AK variations, not to mention G3 and FAL rifles, suitably modified. And sooner or later, all those handguns get replaced with the latest thing and another batch hits the market.