Deadlord is right about the history.  The more I think about it, the more it seems clear that there can NEVER be another Tsojconth or Fazzlewood.  Dungeons & Dragons may stay popular for another century, but there can never be another "beginning".

Same applies to all collectible fields:  Never again will there be "tobacco" baseball cards, never again the beginning of Super-Heroes in Marvel comics, never another first  "Hess tanker truck" or whatever.

Tomorrow's Tsojconth?  Well, it is still out there. . . it just doesn't exist yet (or no one knows it does).  It would have to be something different -- something brand new and unknown that becomes legendary.

Role-playing games already exist -- there can never be another beginning to them.  Another game system would have to be developed -- perhaps somehow related, but it would have to be obscure and not mass produced.   That "new" system would then need to grow into a vastly popular and enduring icon of our culture with fans that continue on and rediscover their affection for it.

A somewhat later example would be Atari 2600 -- video games have endured and we all know how popular/common they are today.  It has created a legacy that traces back (in part) to the Atari 2600 system of the 80's.  Unopened/unused "heavy-sixer" Atari 2600 systems usually fetch around $350.  And there are some very rare, very obscure cartridges that can gather up to $1,000.  These were the "garbage" cartridges -- Atari let just about anyone (it seems) develop and sell games.  A couple oddball, unpopular "junk" games are now the rarest and most valuable of them all. . .  Just because there are enough video game fans who want a complete collection to pay out the ass for them.

So. . . just buy everything that comes down the pipe and keep it all MINT -- you should hit the "jackpot" on something (but not enough to make up for all the cash you spent on the worthless junk    )

If you use comics as an example (and it is a good one), you basically support my theory. Yes, comics were somewhat reinvented. Yes, there are recent issues that are worth a lot of money. But no, no comic will ever be published now or in the future that will be worth as much as Action Comics #1, or Amazing Fantasy #15. Historically, with any type of collecting, the first items produced are worth the most, whether it is Coke bottles, electric trains or RPG's. The reasons are easy to pinpoint. Let's take D&D, and jump 40 years into the future. At that juncture, woodies would probably be worth $10,000, but 3rd edition stuff would be worth a few hundred at best. Why? 1,000 first print woodies were printed. Right now, anything that WoTC decides to send to print is going to have a six-digit print run. And if it does well, it gets another six-digit run.
So 40 years from now, if I am a collector, am I going to pay big bucks for 3rd edition stuff, or am I going to pay big bucks for a woody?
Another consideration is that old modules look and feel old. That in itself makes them appeal to collectors. Compare a newer comic book to, say, Avengers #1 and what is the difference? Modernized art, different paper, etc. The newer comic LOOKS new, and therefore is not nearly as desireable to a collector.
Nope, no holy grails in the future.