There is one indisputably major happening in the '90s, though, that jazz of the future is going to have to deal with--has already started dealing with, in fact. Many of you jazzheads out there are going to truly, truly hate me for going here, but it would be dishonest not to.
Perhaps the hallmark development of jazz in the 1990s was the ascendancy of "smooth jazz."
No, I'm not talking about the pop fluff of Kenny G and Chuck Mangione. What I'm getting at is the soul and funk-based, polished but groove-heavy stuff that has a station in every market. Your George Benson, your Grover Washington, your Joe Sample, your David Sanborn, your Rippingtons, and even your Keiko Matsui. Lest we forget, even the late great Michael Brecker spent some time working in that medium, or at least its ancestor, when he worked with his brother Randy and with Mike Manieri.
Nor am I saying that this all got started in the '90s. Lord knows it can be traced back to the hard bop of Art Blakey, Horace Silver, and Jimmy Smith, and probably began to evolve in earnest with the soul-jazz movement in the '60s, stuff like Lee Morgan's "The Sidewinder" and the early work of the Jazz Crusaders. Benson and Washington made their made their names in the '70s, and the Crusaders peaked then; Sanborn's peak was in the '80s.
What happened in the '90s, though, was that "smooth jazz" grew into its own, pulling elements of all kinds of popular genres. Seventies funk and Philly soul, Motown, soft rock, the innovations of Prince and Thriller-era Michael Jackson, Quiet Storm, R&B, and hip-hop all merged with fusion and acoustic jazz in a slick rhythm-infested stew. It went down safe and easy as you please, yet it still had the carnality and the slinky, ass-swinging feel that's always characterized music much more on the edge.
Not only did this music really develop its own personality during the '90s, but it also became a commercial juggernaut. It's on its way down now, sure, but from about 1994 to about 2002, both white and black middle and upper-class Americans were big fans. At the beginning of the decade, smooth jazz was a commercially viable genre, but the places you were most likely to hear it were on college stations at traditionally African American universities. By decade's end one popular commercial station or the other had changed format to "smooth jazz."
Why does this matter? Well, because commercial music is where the money is, so that's where jazz musicians did session work to make their living! Just as journeymen played on R&B and rock & roll records in the '50s and '60s, they started getting work on "smooth jazz" sessions in the '90s. And whether they like it or not, musicians who regularly play any kind of music will pick up something from it.