When asked again when the Background music functionality will arrive on Xbox One, Phil Spencer the head of the Xbox Division over at Microsoft replied that it’s not a priority, but that they do like the feature and that it will come eventually
“This one is just a prioritization thing with other work. We like the feature.” adding “It’s in the list of things we want to do, just behind other work we are doing right now.”
Currently the Feedback item ‘Play music in the background without Snap’ has over 20000 votes on the Xbox Feedback site. It’s been a highly requested feature as currently you cannot play music in the background while playing a game.
Phil Spencer did however state that the feature would arrive after Windows 10 was integrated into the Xbox, which is coming this fall with the new Xbox One Experience.