Jason wants to know if he can hook up an old Xbox 360 to his XBox One and play older games while daisy chained to the TV. Leo says that the XBox One has a "pass through" feature to watch TV from the cable box, and there's no reason why he couldn't pass the video signal from the XBox 360 to it.
Kotaku has an article about it. The only issue may be lag or latency. But he could also just hook them up directly as most HDTVs have multiple HDMI connections.