Firstly your assumption that Bone hasnt evolved either isn't true at all.... the way conversations operated was unlike any other adventure game.
However, I wont deny I was being overly dramatic and I cant totally fault anything you have said. I guess 18 months ago my arguement would of looked a lot stronger.
But I will raise some things for you to consider;
Only 5.9% of PC games sold were adventure games, and each year that has been decreasing. Of course one could argue that this would occur anyway since the overall number of games being sold is increasing. BUT traditionally I would still argue the number of adventure games is decreasing...... HOWEVER, this in the last 18 months may be false and I will go on to explain that in a minute.
Firstly, high profile games such as;
Broken Sword III
Have all been mildly successful, adventure games of this budget are risky endeavors, even more so then usual. Using the current model, I dont believe this is sustainable and no doubt narrative focused adventure games will be fazed out i.e. I dont expect Dreamfall, Runaway 2 and Broken Sword 4 to do very well. (Clearly, trully original titles that raise the bar such as Fahrenheit will no doubt be financially rewarding, but these games will never be the defacto standard).
Medium profile adventure games.
For the most part this market has never existed before, however the last two years (maybe 3) has really changed things. Despite all belief publisher 'The Adventure Company' owned by DreamCatcher Interactive Inc. has been incredibly successful, the way they have managed to market and do deals with EB, Gamestop, Wallmart is unprecedented. There ability to strike a good deal with retailers has given a voice and a market to medium budget'ed adventure games. Most of the adventure games you have listed were only highly successful because of this company, hell most wouldnt of even been made if it wasnt for this company.
This could go three ways;
1) 'The Adventure Company' continues to be successful for a good number of years and we all live happily ever after and I only suffer from accute paranoia.
2) 'The Adventure Company' for what ever reason is forced to close, if so then my concerns are real and my $20 may be the only thing that saves us..
3) 'The Adventure Company' continues to be successful and sustainable for a while, but follows the well documented life cycle of a video game genre and decreases in popularity forcing developers to continually lower their budgets until this bracket of medium budget'ed titles is no longer sustainable. In which case, my $20 may save us all, but I still suffer from accute paranoia.
If medium bracket'ed games are no longer viable like I believe large budget'ed titles aren't already, then it relies on small (and tiny) budgeted games via online distribution. Small teams of 5 or 6 people could develop their games for next to nothing and then release them via online distribution, larger teams of say 25 people could do so as well. Those "amateur" developers of teams of like 1 or 2 you mention could work a little harder on there title and release it via this model as well. Everybody wins, however if the "online distribution" model completely fails for independant developers than I believe all is trully lost, but again, I might just suffer from accute paranoia.
If Telltale is highly successful I expect there to be a large number of copycats. Also this method isnt as limiting as it may seen because as Internet connectivity increases so does the size of the game possible to distribute.
However one thing you have brough to my attention that is of EXTREME interest to me, is your mention of the Nintendo DS.
Japan has never been a fan of adventure games, the closest you got was Shenmue and Hentai games (some are actually pretty damn good, Kana: Little Sister all the way!!!). However now with the DS, adventure games to an extend are coming in genres we have never seen before. Now here is what interest me, perhaps with the Nintendo Revolution and its pointy and clicky remote we will see a new breed of adventure games.... but this is just me being hopeful...... but there is a possibility especially if the DS continue to be successful!
So yes, perhaps the saviour of the adventure games genre will be the Japanese, perhaps it will be Medium budgeted titles or perhaps it will rely on smaller online distribution (with a chance to expand in the future) or perhaps DeadMeat is right and I am just paranoid and all methods are sustainable and all will work concurrently. Honestly, 2 years ago I wouldnt of even pondered over this, but DM's oppinion especially in the last 18 months does certainly have merit.
NB: I would rather not even mention CSI and Law and Order games, they are a stain on the adventure game genre..
Even if the adventure game genre completely
collapsed these franchised games would still be produced and be successful, thus they are more akin to cockroaches surviving a nuclear bomb