Hi,
I think that "rock music" will eventually add a "bass guitar" to its orchestra design ... just like the electric guitar.
Those two have been developed a lot better and further than most other instruments, specially when the synthesizer is nothing but a replacement for another instrument in an orchestra.
In general, from my perspective, classical music has not had the repetitive and contextual basis that rock music (and jazz!) has defined for itself ... and this creates more possibilities for the future by the time the two mix and match and learn to play together.
There is a thread, or group of folks, that do not believe that anything that is "popular music", of which the "electric" contingent belongs to and is a part of, will EVER be a part of music history ... and I think that is incorrect. Music has always shown improvements, and additions and other factors in its history, and I think that rock music will help a lot of new things in the future ... and the likes of work, like Mike Oldfield, guitar over the orchestration, will be more and more visible in the future. Unffortunately, most of us will be long dead and gone to find out about all that ... but if something like that does not happen, "classical music" will probably die after 500 years! Replaced by music that is more forceful, has more personality, and clearly defines the human nature and potential a lot better than before ... because it allows emotion with vocals, something that most classical music has very little off, and has had 500 years to address, and didn't!
I wonder if we are thinking of slapping as some sort of process that belongs in the music ... and I have always thought it was more of an accent than it was anything else ... weird to see it thought of as a process that belongs in music!