Hey colterphoto1,
Unfortunately, it isn't going to end at 9.1
I read an article where the author was saying that audio really won't get good until 12.1 surround kicks in. Yes, 12.1 surround.
According to his placement chart you would have a center, a left-center and right-center, a left and right, right and left front prescence (to the side of your listening position and slightly ahead) a right and left rear prescence (to the side and slightly behind), a rear left, right and center channel speaker. Add in the sub for the .1 and you got yourself a fully encompassing field of sound and divorce papers from your wife.
I hear the Terminator 3-d ride has true 64-channel sound on it. Of course, Jim Cameron can afford something like that.
Sorry for the off topic rant there.
I haven't heard anything about new audio formats (outside of the DPLIIx that came out on the newer receivers). I don't see radically new sound formats coming out in conjunction with HD-DVD (is it true what CNet said about HP declaring Blu-Ray the winner?). I don't think people will take to kindly to having to upgrade their DVD players (and possible TVs if 1080p starts making a charge) with DVD still being a relatively "new" technology for the majority of consumers.
As far as upgradable receivers, I know Onkyo has that new 900 model out that is both software and hardware upgradable. Of course it comes in around $4,500 so you are definitely paying the piper now for future technology.