XBOX doesn't compete with the channel 'partners' in the way that PCs and tablets do.
So yes, XBOX will be safe (or at least be allowed to live or die on it's own merit).
Surface quickly - and imho rightly - became the preferred Windows device, which annoys the other Windows PC vendors. It was a rude shock to them, and they had to lift their game, or suffer.
Now that Dell, HP & Lenovo are all making excellent hardware, perhaps Surface isn't needed anymore. It's achieved what it was meant to achieve.
Personally, I reckon Surface will be retained for at least one or two more generations, because MS need to get the ARM devices into the market. A Surface tablet running Windows-on-ARM? Here, take my money.
But after that?