At the moment, it seems the cost of bandwidth is sinking faster than new games are growing in size. And making the games yet bigger again is hitting some economic limits on the game maker's side. If you've got broadband, you've probably got enough bandwidth even without special deals. (And yes, I know that's not 100% true, which is why I said probably, but we've got at least another year and maybe two or three before this is even remotely a big deal for the XBox720, during which the bandwidth situation should continue to improve.)
"I don't know , I haven't noticed bandwidth caps getting much better."
Yes, a lot of people have gotten so cynical they haven't noticed, no sarcasm, but many consumer internet connections over the past few years have simply gotten better, without much fanfare. I believe right now my mid-grade Comcast connection is now primarily speed limited by my wireless router, rather than the Internet connection itself. This was not true when I signed up for it four years ago. I still have a 250GB/month cap (which I still only come about 33% of the way to using) but I wouldn't be surprised that grows sometime before the XBox720 gets out there.
It seems like games have been shipping less video as the in-game engines become more and more capable. Game companies were already straining to fill the disk in this generation, I think in the next generation it is very likely to be game company resources that are the limiting factor rather than bandwidth concerns.