on the contrary... i think the adventure game is in for a comeback...but slowly.
What was needed was a good adventure, and Syberia was good. It sold very well too and got wide acclaim in the games community.
Now, there are in the pipeline: Syberia 2 (october 2003 and looking fabulous), Runaway (which looks absolutely fabulous, just like playing a cartoon, and which got top scores in all countries were it was released), Broken Sword 3, Sam & Max 2 (Lucasarts), Longest Journey 2, Full throttle 2 (Lucasarts).
Not a bad line up.