As I think I said previously, just wait a couple decades and things will probably change.
If anything, I predict a resurgence of upright bass, due to the rising respectability of the bass and the spread of school orchestra programs.
When I was growing up, it was hit-or-miss whether a young person could get any instruction on bass at all. Many schools treated the bass as the instrument that anybody could figure out on their own and play well enough to thump along behind the band. People who became jazz bassists, like me, often had their training in some other instrument -- cello in my case. I know other bassists in my locale who had similar experiences of switching to the bass from other bass clef instruments -- cello, trombone, tuba.
Where I am now living, music is flourishing in the schools. Students are learning upright and getting serious classical instruction. There is no corresponding opportunity for kids who play electric bass. As a result, the upright players will have first pick of chances to learn jazz. If young upright players are favored for those learning opportunities -- in school groups, low profile gigs, etc., they will gain the knowledge and experience that lets them advance.
So I think the challenge for electric bass is not merely to prove that the bass is functional in a jazz setting -- because any instrument is. The challenge is to figure out how to provide electric players with the kind of training that upright players take for granted.
Meanwhile, I don't think the preference for upright bass is simply a matter of traditionalism, enforced by the "jazz police." Jazz is a moving target, and a competitive scene. It's a mistake to think that the "upright sound" is encapsulated by old recordings. For example, I make extensive use of the bow when playing jazz, although there is relatively little bowed bass on those 100 famous recordings.
By the way, +1 to Pacman and Jim Campbell. In my view, jazz is about knowledge, because the work of the past happens to be of lasting value, but it is also about finding a conduit from your ears to your hands, through your brain. That can be done on any instrument. It's a bit harder to work in the scene if you don't play a traditional instrument, but that hasn't prevented people from playing jazz on violin, cello, french horn, etc.
