While the instrument may be gone in some of these bands, the sound clearly is not. this genre of music doesn't drive like the late 80s when the bass was the beast. The White Stripes for example, just use a sub-octave pedal for the intro to "Seven Nation Army" (and others) and as was pointed out earlier, Rush, for a selection of songs used a keyboard instead of the bass.
I think there will be lots of room for bass players in the future and the uber-talented bass players will still be the back-bone of sojme bands, like the Chili Peppers and Primus.
And lets admit it - Metallica has never been as good since Cliff Burton died.