Yeah, hard drive speed isn't increasing that quickly. I think we are waiting for the next gen storage medium. From what I remember, they are working on optical storage akin to a homomatrix cube in star trek. Of course the actual storage won't be a holomatrix but the principle is the same: information stored and acessed using light.
If I remembered where I read the article I would post a link. Oh well, just thought I'd mention it.
SATA II cabling is backwards compatible, so its worthwhile to consider using them even if you're using a SATA drive, nothing worse than upgrading some point down the road and having a hidden glitch due to the wrong cables.