MSFT can't afford to let the console go back up as sales will tank. They are banking on making money from software/XBoxLive and taking a hit on hardware vs sony making money on both.
You essentially hit it right on the head.
Also, M$ is counting on releasing Windows 10 to the XB1 in 2015. They have announced that it will also release on PC and Windows Phone in 2015. So, their plan to have a unified operating system will be complete by the endo of 2015. Why does this matter? Well, they will then have platforms available in every part of the home to push not just XBL, but Office and XBox Music/Movies/Games. THey have already started rolling out package deals to get all of their services bundled together.
So, losing a little money on the console is an acceptable part of ensuring that they gain access to as many homes as possible.
It is near the end of the end....