4 string basses are never going to become obsolete. Too many people still use them and pretty much nobody starts out playing bass with anything other than a 4 string. Likewise in response to the comment above, 5 strings will never become the standard, but the comparisons used are not particularly good - "'Cookie monster' vocals detuned Nu/Rap metal tripe" - Now I see what is being said here, but having once been a 5 string user in a metal band, it is all about how you play the thing and how it fits in the context of the music which is true to any style and any bass be it 4 string, 5, 6 or people who go beyond that! Ask Dood if he could do half the stuff he does on a 4.......I'm sure he spent all that money on a 7 string for a reason
In my eyes, very little will change from where it is now. As for bands like The White Stripes, I am not a fan at all and I would suggest a big reason they have kept themselves as a 2 piece is for the commercial value that is attached to novelty factors. If they are not already dying out then they start to soon. And lets face it, they have hardly spawned a whole breed of bassless bands have they? And when you watch a band live, how empty does it sound if the bassist happens to drop out or have technical problems on stage?
We are not in any danger whatsoever.