Answer to the question: No, it absolutely doesn't become obsolete.
I'm playing some 4s (JB + JB FL, JP, P, MM), 5s (TRB, MM), 6s (TRB / TRB-P) and all of them have 19mm string spacing and are played almost equally often.
Depends on the music / the songs, which one I chose. Playing R&B, Funk...