"Behind the Curve"...
Here is how simply I see it... I buy games at their low, which I call internally staying Behind the Curve. This is generally a few years behind a given system and then the games start to go back up, but varies based on factors that don't really matter to me or need to be defined. I just track the prices, which is super easy with the internet these days.
I remember when you could by Atari 2600 stuff in large lots cheap, as most of us here do... around the time the PS3 came out, Atari stuff was really sagging in price, PS2 used stuff went up like cwazy as many could not afford PS3's now had access to SO many used PS2's flooding into eBay, second hand game stores, and pawn shops.
I don't have time to be comprehensive with this explanation/analogy, but I just want to point out that all systems and their games sag in price and then come back up. Some things seem to fall in value continuously (like boxed Vic-20's) and some things just rise in value continuously.
The point is that I just see Atari games as back on their rise out of the low-price sag. In this age of excess, where collections are fashionable beyond the scope of actually using them of course any social icon like the Atari, or even video games in general are going to become more expensive.
Don't forget that a large group of people are collecting for the sake of collecting at a social level. Then this is no long the "in" thing to do, those collections will end up right back on eBay and like Beanie Babies, you won't be able to give them away. Just don't think that everyone who has a collection of Atari games and systems (or any games and systems) isn't going to move on the next big social thing next week. Sure some people will learn about them and become genuinely interested long term, but many will not.
Example: PS2 games are at their low for sure. For the last couple of years I have been buying specific PS2 games I think I would enjoy. I have doubled my library of PS2 games for SO little in the last 2-1/2 to 3 years. You can always find good deals if you watch of course, but I am talking mostly about averages of course.
If we are indeed in a bubble, and you want to know when it will pop, you have to know why it exists...