Major Nelson confirmed during his PAX podcast that external storage support is coming, but he didn’t know when it will come through. It will be a feature that is not supported at launch. This seems to be the latest in things that are not going to make the Xbox One launch. (The support for external drives feature was first announced back in May.)
It remains a mystery as to why this feature will not make launch, but we can’t see Microsoft not offering this feature soon. Still it is surprising that a feature like this will not make launch.
By contrast, the PS4 does not support game installs like the Xbox One does, but it does offer the ability to replace the hard drive with a larger one if the user desires to do so.
Get more info from Major Nelson here.