Well if it weren't for large corporations like Wal Mart and Gamestop who sell video games, I'd say it would be digital downloads. But thank goodness for them because I like the idea of going to stores to pick up those cases with my discs haha.
I really don't know what the next big thing in gaming will be. I can't even take a guess. Although I'm sure next generation will continue to put focus on motion sensing, downloadable games (although not large retail ones), and social online networking (although I can't say I'm too happy about this one either. Fads of this generation actually turned out to be the heavy focus on HD graphics haha. Who would have guessed.