I agree with Jarek. The gameplay model was broken from day one, and nobody ever really fixed it. Even in it's prime, the gameplay was only vaguely fun.. it was more the satisfaction of solving a puzzle more than anything. The weaknesses in the gameplay soon became all the more apparent as more open-ended gameplay came onto the market in the mid 90s (RPGs, FPSs, etc). Adventure developers never stood up to this challenge, instead they kept churning out the same old tired game.. something that they are STILL doing. Just play a demo of the most recently released adventures like Black Mirror, Syberia 2, or Moment of Silence.. 10 years and absolutely no change, except for better graphics. There were the occasional attempts to revolutionize, like Access Software's Tex Murphy series, but there was never any forward momentum from a large number of developers. This of course all led to a decline in sales, which also meant less development money. So even if said adventure devs wanted to try something different, they didn't have the dough to do it anymore.
In addition to the financial situation, they find themselves facing the question of relevance. They are in a situation now where other genres have incorporated their genre's best elements (story, character interaction, etc.), while leaving the bad stuff behind. So is there really any incentive anymore for the average gamer to pick up an adventure, when they could instead get the latest action-adventure or RPG-adventure hybrid, and get twice as much game?
Two things adventure devs need to do.
Reinvent. Starting with the puzzles, which is essentially the key gameplay element. This would mean complete non-linearity. multiple solutions to puzzles, and no more of the single solution trial-and-error BS. A complete move to 3D will also be needed in the long run.
Survival. they need to consider moving into online distribution for the time being. In other words, selling only to a small hardcore audience and cutting out publishing costs and what not. Revolution and the guys behind the Tex series want to try this, and it might just work. They might find that this is the future of adventures, and forget about Reinventing.
But still, a total renaissance of the genre will take a long time. And like I said, there is a high chance it will be seen as redundant, as FPS's are already well on their way down the road to reaching the perfect action-adventure hybrid, which the adventure genre would JUST be starting to travel.