Recently confirmed by @XboxSupport on twitter, if your account has been banned you will lose the license to any games attributed to that account.
@dohertymark If your account is banned, you also forfeit the licenses to any games that have licenses tied to it as listed in the ToU. ^AC
— Xbox Support (@XboxSupport1) June 14, 2013
This news comes as yet another blow to the perceived attack on gamers...
There have been multiple updates to this article, each with varying importance. However, the final update sums up most of it.
"Larry Hyrb, aka Major Nelson, in a video interview with Reddit, has clarified banning and other tough topics. Within one minute of the video he is asked whether banned users will lose access to their games, in which he responds “absolutely not.”
So it looks like Banned users will not lose their disc based games. We will see for sure how the rest of it shakes out once the full Xbox One Terms of Service are released. So until then, keep calm and know that the people at Microsoft, while not always on message, are not stupid.