In short, no. Xbox Music will not offer Xbox One owners a free, ad-supported music streaming service.
The news comes from Albert Penello who earlier today told prospective Xbox One owners that Gold Subscribers would not have to pay an additional subscription to Xbox Music; instead, they'd have to sit through periodic ads.
Turns out that's false. Shortly afterward, Penello took to Twitter again and posted the following clarification:
I was wrong about Music on XboxOne: You get 15 free song plays then need Music Pass for ad-free streaming. No ad-supported streaming. Sorry!
— Albert Penello (@albertpenello) November 6, 2013
So looks like Xbox Music will require an additional subscription after all. Classic case of the left hand not knowing what the right is doing.