We're excited to announce that we've fully migrated the Xbox Forums to their new home, here on the Microsoft Community forums!
As of today, going to forums.xbox.com will redirect you here to the Xbox area of the Community forums. We've moved all of your existing threads over so you can continue and start conversations with the new forums experience.
We sincerely appreciate the feedback you have provided over this transition and can't wait for you to check out the new Xbox Forums!
Basically no, you still have the digital games, follows your profile, so if you sell the xbox, you still own the games, and they cant play it unless they want to keep your profile as home, which would not do as they want thiers to be home.
That was a rubbish explanation, but the simple answer is no, you cant sell digital copies...yet at least.
I would highly recommend deleting everything from the console before you sell it (but keep your saves in the Cloud). This way, if and when you get a new console, you simply designate that as your new home console and re-download everything.