Straight from the mouth of the man himself, Phil Spencer says the Microsoft team is "working on" bringing original Xbox games to the Xbox One. Destructoid says the statement was made in response to a fan on Twitter...

Don't get too excited yet, as it was nothing short of a miracle how the Xbox team managed to emulate an entire 360 on the Xbox One to begin with. I would imagine bringing the Xbox in would be a whole other beast to deal with, despite it's age as a console. Let's not forget that Spencer has promised MANY things for the Xbox One that still have yet to be implemented. The biggest example I can think of is mouse and keyboard support. 

Still, if they manage to make this happen I wouldn't complain. Can anyone complain about more cheap games they can play?