I was just reading an article a few days ago about where surround sound is going to be headed to. They were saying in the year 2025 they want to make 22.2, so 22 speakers and 2 subwoofers. There will be 10 speakers sitting at ear level in a surround sound arrangment, 5 speakers at knee level in surround sound format, and then 7 speakers above your head also in surround sound. Then 2 subwoofers placed in the room.
The deal with surround sound now is I'd say 95% of the content out there is 5.1, then maybe 5.9999% in 6.1 and I dont know of anything in 7.1, but I left some room for error. The reason for that is space to store the data. There just isnt enough space on a 4.7 GB dvd to hold content over 6.1 and a high quality movie at the same time.
Now that we see things going to HD, the disks are being able to hold larger data files. HD DVD is 15GB and Blu Ray DVD holds 25GB. They are trying to create quad layer disks as well. So HD DVD would then hold 60GB and Blu Ray holding an amazing 100GB. The reason they are upping it is not for sound quality, it's for HD content.
A HD signal at 1366X768 takes 1.485 GB/second. So if you have a 2 hour movie it HD that needs you need 10.692GB of space for that. Now that the Blu Ray and HD dvds are out, they are going to 1920X1080. That uses double the space, so 2.97GB/second. Therfore for a 2 hour blu ray the disk needs at least 21.384GB of space. (Side note, HD DVDs are not 1080P or 1920X1080. they are the standard 1366X768, as soon as they have the quad layers coming out they will be doing an upgrade to 1080p rather than 720p)
So just the shire data it takes for HD content is what is holding back sound. Another little side note is at the year 2025 when sound goes to 22.2 surround sound they are also going to be upping the resolution for HD content. It is supposed to go to 7680X4320, and each second will take 24GB/second....PER SECOND thats amazing.
edit: here is the link to the sound and vision article if you are interested.
http://www.soundandvisionmag.com/features/1719/beyond-hdtv.html
Edit: fixed grammar and spelling....happy?