Do not see why MS could not just either sell SD card or give out an approved list. You buy one big SD card, go to Gamestop purchase your game, they put it on the disk. Then you can either install the game to a Solid State HDD in your Xbox or leave it on the SD card. Also with Apple showing how having a App Store is the way to go, you will be able to just purchase the game online and download it to your drive or your SD card.
For people who want backward compat, you can purchase a cheap external drive from MS (yes I know they do not do cheap) and then be able to play those games. Also this will give you the ability to install the games on yoru HDD or SD if you want.
MS can definitely cut the Disk Drive and the savings can go to a decent size SS HDD. They already have all this streaming going on so having a physical drive isn't neccessary especially since App stores are changing the way people think about how they get their software.
