Given that XBox has been marginally successful as a business and was greatly dependent, for its success, on the dominance of the PC gaming platform, I don't think XBox is Microsoft's ace in the hole.
Just as an anecdote: I used to stream my Netflix through my console (PS3) as my primary usage of said console. I got so frustrated with having to do Software Updates, seemly "every time I turn the bloody thing on!", just to launch the Netflix app that I went out and bought an AppleTV. My console is no longer even connected to a TV or power cable.
I did a similar thing because I was almost exclusively using my PS3 for Netflix, but my motivation was mainly because the AppleTV runs at ~6 watts and my "fat" PS3 runs about 170 watts at idle and we were always leaving the damn thing on. By my calculations, my Gen2 AppleTV paid for itself in electricity savings about 3 months ago.
I keep it because it's my only way to play discs on my TV, but it's seldom used, and PSN's massive security blunder left a bad taste in my mouth.
http://www.statisticbrain.com/netflix-statistics/
The figure quoted is 50%. Also bear in mind that it's not exclusive, and it's counting all supported game consoles (e.g. including the Nintendo Wii).
My guess is that TVs with built-in Netflix streaming support and AppleTV (now outselling XBox http://macdailynews.com/2012/07/25/some-hobby-apple-tv-outso...) are hurting this.
Given that XBox has been marginally successful as a business and was greatly dependent, for its success, on the dominance of the PC gaming platform, I don't think XBox is Microsoft's ace in the hole.