I think that the word "classical" would have to be defined satisfactorily before there could be any discussion of "its" future. (I would predict that without a satisfactory definition, the future of this thread will be that it consists of fuzzy and contradictory claims full of sound and fury, signifying nothing.)
But since I'm first, and writing this will keep me from my real work (!), I'll attempt to make some sense of the word "classical." It is first of all a term that has been used to describe the various musics of about the past eight hundred years or so. (I don't think we need to fash ourselves about the the term's use to identify a period--nobody goes into the classical section of a music store expecting to find only Mozart, Haydn, Gluck, and Beethoven.) It's not so much its broadness that's an issue, though it is certainly broad, its the variety and complexity of the items within its scope.
Second, it's a term that is often used as if it were narrow. That is, as if "classical" identified a certain sound or style. I suspect that tgreen may be using it this way, as s/he has called it a genre. That's not technically wrong, but it suggests that classical pieces have something in common stylistically. As if "classical" were equivalent, as a term, to "rock" or "jazz" or "country western"--or even as if it were equivalent to "metal" or "hip hop." Since its historical range (800 years) is so great, it will contain a greater stylistic variety than a term that covers only 80 years, or 8.
So how is it possible for a term to include Gregorian chant and Annie Gosfield? I think because it identifies an attitude, an alignment with the materials that respects them for themselves regardless of (or at least in addition to) the effects they can create. Popular music, broadly speaking (!), views the materials as merely tools to create the effect (the effect being to galvanize the muscles near as I can figure!). Classical music views the materials as things valuable in and of themselves and so creates an often bewildering plethora of effects. (There is more purely musical variety in five minutes of John Zorn, for instance, than in all of rap. That is not to denigrate rap, by any means, just to point out a difference. Rap's not going for variety, Zorn is.)
But Michael, you'll say (if you remember my real name, anyway), isn't John Zorn a jazz artist? Yes. That's why I used him. His music confuses record store managers. You can find his albums in classical, in jazz, and in rock. Think of all the arguments you've ever heard about whether classical is better than pop. The pop music that will be put forward in those discussions will share some of the qualities that classical pieces share, will contain moments where the pitches, harmonies, timbre, rhythms, combinations of instruments seem to have an importance beyond and above making people tap their feet or bob their heads. (Not, I hasten to add, that tapping and bobbing are bad things! They're just not the only things. When they're treated as if they were, however, you have pop music.)
So have I just worn you all out? Or confused things before the discussion can even begin? Oh, well. You are all free of course to continue using "classical" as if it defined a style, as if it identified a music that's in the past, and talk about the future of performance, if you like. (Which is what this thread could easily turn into: how likely is it that the music of Brahms and Mozart will continue to be played in 3008?) Or we can talk about new classical music. About laptop ensembles, live electronics, new instrument techniques as well as new intruments, about electroacoustics. (Problem there of course is that most people who attend symphony concerts--and who buy classical CDs--is that the classical musics of 1988 or 68 or even 38, are still pretty much terra incognito. The arguments among many classical listeners are still about tonality/atonality (an argument that was really over by 1936), or consonance/dissonance. So I wonder how much we will be able to talk about the future of classical music if we don't even know much about its last fifty or a hundred years?
(Hey, I'm just sayin'.)
I really don't know what the solution is.