I'm sure there are many factors, but I agree with the theories about people turning their attention away from hoarding ARs and AKs.
Though minor, and a single data point, my LGS supports that. When I was in there last week, discussing a few things with them and having some FFL copies emailed, they (owner and his gunsmith) said they hadn't sold an AR since January, and the last AK sale had been about six weeks prior. However, they've had more sales and inquiries about lever actions and their small assortment of mil-surps than in the past few years.
Another thing they've seen, but I haven't seen people talking about across the country, is a huge spike in new shotgun sales. Plain-Jane Remington and Mossberg pumps, in particular, have made up about 50% of their firearm sales for the last few months. (Very unusual for this part of the country.)
And, again, I don't know how well it fits into the 'big picture', but they've also had a big spike in people bringing in "grandpa's old rifle" (usually an abused mil-surp) to see if it is shootable, get it fixed, and/or to see what it shoots.
I'm no gun shop lizard that hangs out all the time and sticks my nose into other peoples' business, but the LGS knows me just enough to know that I like the mil-surps, even if I don't own many; and that I know the cartridges better than the actual rifles. So, it's fun when they ask for my advice if I happen to be there for something. Lots and lots of Mauser 98s, Arisakas, and Berthier carbines coming out of closets around here; with a surprising (though still small) number of 1888 commission rifles...
Perhaps "grandpa's old rifle" is spurring interest in more mil-surps, for some of the shooters. ...Especially those that discover that they can't get ammo for what they already have.