MKall, you suggest that other toylines styling don't change as much as Transformers do. I'll admit that is true to some extent, but look at GI Joes from 10 years ago, compared to what they are now. Back at the turn of the Century the original 80s construction and style was still very popular in the brand, and even the updated designs of the Joe Vs Cobra line could still look like they belonged with that era of figures. Now, post-25th Anniversary figures, there have been a huge number of changes to the design of the toys, making them far more "realistic". Same sort of thing has happened with superhero toys, although the Marvel Legends line took a big huge step in the right direction early on.
As to the matter at hand, I agree that Classics/Universe/Generations types will probably increase in value and think it is quite likely that many of the more sought after 3rd party items will remain so for collectors in years to come. City Commander still sells well, as do a number of other 3rd party items which were released years ago. The problem comes with competition, and replacements. For a time Henkei Megatron was THE NeoG1 Megs. Then the United version gave folks who missed it a chance to get in on the silvery goodness. Hegemon seems to be widely regarded as the best Megatron out there now for a Classics look, but who is to say that another 3rd party, or Hasbro themselves may not take a look at the character in the future and create an even more definitive version of the character. Same goes for MP01. It was AMAZING when it was first released, but by all accounts, MP10 blows it away. Because the G1 characters and their designs are so iconic, and collectors tend to continue to try and upgrade to the "best" version of a character available for their collection, any newer toys of similar designs or characters might reduce the demand for what we currently see as "must-haves" for our collections.
As to the youth of today...yes, Beast Wars, Armada/Energon/Cybertron and the like may see a resurgence in years to come. I wouldn't be all that surprised to see a new take on some of the more popular characters from these franchises in 10years time, BUT I think the influence of the Michael Bay films will be more noticeable. If we're lucky, for a time it will probably die down a bit with the endless Bumblebees, but there will probably be a very high-quality intricately designed version, possibly with a wee plastic Shia The Beef, around the time all those kids today are getting better paid jobs.
I'd also expect that aspects from all these iterations of the TF Brand will be included or will influence the ongoing design and direction of the franchise as we move on. We already see that with Airachnid in Prime, who is clearly inspired by Blackarania, who many of the kids who say the 2007 movie, and whom the show is aimed at will never have even heard of.
Finally, as to there being no G1 media to advertise the original characters any more...well, there is the IDW comics. The designs are kind of different depending who is drawing, but there's little denying the current books are definitely more based on the G1 story and characters than any other series, with very little inclusions from other eras. Now, as to whether any kids are actually reading those comics, that's a completely different question.
assembling a Neo-G1/TF:TM cast. Please PM if you have (or know of) the following at a reasonable price: Classics or Henkei Prowl, Astrotrain, Ramjet, Skywarp, Sunstreaker, Sideswipe, Blurr, Perceptor, GDO Wheelie and Springer, or 3rd Party Motobot Arcee, FP Springer, iGear Ratchet and Ironhide, City Commander (and/or Ultra Magnus), Starscream (deluxe) Coronation add-on, or Spike and Daniel in their Exo-Suits.