Being that there's somewhat of a format war (though 90% of folks are behind BD as the winner, and rightly so) I can actually imagine prices on discs being competitive with DVD to get people buying. But there’s no real word on pricing yet.
From my own experience with HD movies off of satellite and cable that I’ve stored on DVHS (and slowly being archived back to hard disk) I've noticed that it's very hard to go back to DVD. It's not a night and day thing like from VHS to DVD, or even LD to DVD, but the differences in color reproduction and detail are undeniable. Once you’re used to a certain image, and are presented with something that doesn’t fit with those expectations, it becomes a major distraction. In the next few years, as 1080p displays become more widespread, the gap will continue to grow, and the HD disc formats are going to become important for the sets.
When BD hits, it will also support hi resolution lossless audio formats. That will be a huge advance over lossy Dolby Digital and DTS. It’s good enough that it will actually force a revolution in audio quality coming from the studios and supported in the theater. Home devices will actually be able to support playback at quality levels mixers aren’t even working at for masters. Pretty cool.
Aside from audio and video, there is the storage capacity element and what will surely be a crapload more interactive garbage thrown into the mix. It not something I’ve ever liked much so I’ll continue to ignore, but it will be there.
I’m going to probably be a lot more selective in my purchases this time around. I repurchased just about everything I owned on LD with DVDs. But I don’t see a need to do the same again for a lot of the catalog titles I own. If I glance at my collection, there are literally dozens of discs I haven’t opened, including such pure uselessness as Spy Kids, The Smokers, Ruthless People, Solaris, and on and on. It will be new releases and titles I actually value this time around, instead of every single movie I ever expressed a remote interest in seeing at some point in time.