Right now there's a big spotlight on all things video games. It'll move on.
Truly rare stuff will increase in value as time goes on; there's no helping that. The common stuff will fall.
In 10 years the few people who love video games will still want that rare game. The millions of fly-by-night, me-too insta-collectors will no longer give a shit about SMB3, and its price will plummet.
I agree with pretty much everything you said. However, I think games with mass appeal will maintain some value. SMB 1-3, Punchout, Contra, Super Mario Kart, Super Smash Bros, things of that ilk will not lose value until most of us are dead. Any child of the 80s to 00s will remember these games fondly, and at some point will want a copy to share with family, grandkids, and whoever.
That said, some of the hyped-up rares, like Hagane, Little Samson, or Flinstones: Surprise at Dino Peak have appeal to only hardcore or insta-collectors. These games are far more common than people let on, and once the market goes away, their prices will crash. Collecting-hysteria is the only reason these prices remain high.
TG16 is a harder situation to understand. There are probably a few reasons to start getting into TG16 later in life. My thinking is that it has wider appeal to the elitist collector - which can and sometimes is the same as an insta-collector. Which raises the question, are the prices on midlevel rares just hype? Games such as Soldier Blade, Neutopia II, Jackie Chan, Air Zonk, and etc, seem in line for the current level of demand. My question is, how much of that is just the insta-collectors branching out into TG16 to increase the obscurity of their collection, and how much of it is actual low-supply side economics? Its hard to tell what TG16 demand will be like in the future. I'm just happy my collection is mostly where I want it.