I don't think there will, necessarily, ever be a cap on the really rare titles. Games like Stadium Events, NWC, Little Samson, etc... will always be worth money and likely increase in price, to those top-tier collectors. But, I do think we're gonna start hitting the ceiling on a lot of other titles. Just for example, take a few moderately priced games, something like Sunset Riders, Turtles in Time, King of Dragons, Knights of the Round, etc... Think about those $50-$100 dollar titles... I don't ever see those games being $200+ dollar titles. Eventually, things are going to peak. I think we're already kind of seeing it. Eventually, people our ages are going to finish collecting or decide they don't care anymore. And yes, there will always be interest in retro games, but it just can't possibly keep going higher, at least not the majority of games. Video games are nothing like baseball cards, comics, classic cars, etc... Wall street bankers and high rollers are usually spending big money on stuff like that. None of them are out trying to gobble up video game libraries, hoping that the value increases times ten.
It's similar to something like vinyl. There was a huge boom in vinyl, 10-15 years ago because all of the people who grew up with it wanted their collections back. A lot of records which actually sold a lot of copies and had plenty of them manufactured were selling for pretty decent money, despite being extremely common. Now, you can walk into any vinyl store and buy 90% of their titles for a fraction of what they were selling for 10+ years ago, unless it's something really, really rare. Of course, there are still people interested in vinyl, but like any hobby, when the age range of people who grew up with it start to finish their collections, get their fix, or get out of collecting and decide they don't care anymore, prices stabilize and or drop a bit. I'm not psychic, so I can't say what's going to happen with video games, but I can't see it rising and staying hot forever. Same thing happened with baseball cards and comics. They were huge through the 60's, 70's and most of the 80's, so then, a lot of people gobbled up comics and baseball cards all through the 90's and then those markets just crashed. And now days, those hobbies aren't anything like they were 20-30+ years ago. Sure, there's still interest, but nothing like there used to be.
I only see video games sliding down, other than those ultra-rare titles. Especially, as we move further with technology. A majority of people would rather emulate or own games on the virtual consoles or buy crap like the NES mini and such. People like us at NintendoAge are the minority. Most people aren't keeping multiple retro consoles around with a CRT or Framemeister for HDTVs. And even if Joe Six-Pack decides to get ambitious and hook his old consoles up to his HDTV, he's probably going to decide it looks like complete ass and will probably just go the emulation route anyway. So will games and the hobby always hold value to us and the community here? Of course. But, there's still plenty of casuals and tourists out there buying retro because it's hot right now and that's keeping prices steady. Give it a few years and those suckers will get weeded out and the fire will die down a bit. I'm, by no means, saying everything is gonna come crashing down and we'll be buying 99 cent NES carts again. But, it's not gonna ride this high wave forever. It's just not. No market does.