Xbox One early adopters will be limited to only the 500GB of internal storage found in the console after it was confirmed external storage support will follow post release.
"That feature will not be there at launch because the team is working on some other things, but it definitely is on the list," said Major Nelson during a podcast recorded at PAX last week.
He added: "I don't know when it will come in though."
The feature was announced back in May, with the promise of storing downloads and game installs on external drives.
PS4 doesn't support game installs on external drives, Sony Worldwide Studios boss Shuhei Yoshida has confirmed, but the console does allow users to swap out the 500GB internal drive with a larger capacity disk if required - a level of customisation not afforded by Xbox One.