The key thing here though is that the consumer then will have the choice. Do I go for the $250 model of the $400 model and then 2 years later decide to hold on to what they have or upgrade or wait to upgrade when the upgraded model goes down in price? I think the key thing will be in how seamless they message that regardless of which Xbox One System you buy, you Xbox Live Sub will work, Your Xbox One Controllers/Wheels will work, Your Xbox One games and your Xbox 360 games will work backwards or forward.
I think for devs, especially for PC devs, this will be something easy as PC devs are already use to this. They make a game that is scalable. The difference will be that the game once it begins to boot will do a quick check, if it detects the low end Xbox One, the games settings will automatically scale down to 900p/30fps/8xAF, 2xAA etc. If it detects the mid-range system or high end system it goes to whatever those presets. On PC the user has the ability to adjust resolution and a long list (depending on game) to customize it to the users liking. For a console, it needs to be simple, so it would be pre-set's type of configuration.
The game loads, it runs a quick compatibility and the settings are loaded for low/mid/high/very high or ultra. This would allow the scalability as future versions of systems come out or games get patched with other pre-sets. Right now I can take any one of my PC games and scale the game from 720p to 4k without an issue, why would it be a nightmare for developers as some are suggesting?