It definitely benefits Xbox owners if there are more gamers playing Microsoft's games. Could lead to more development deals, and more games. Which is the whole point really.
Very big "if". Very hopeful and very naive "if".
Thing is, we've already seen how Microsoft behaves in this situation with the XBox 360.
PC gaming used to be a big market for Microsoft. When their PC market was stagnating and they saw lucrative possibilities on the 360, they closed studios left and right and made 360 their focus. Way back with games like Shadowrun I remember people saying "don't worry. Microsoft will still focus on PC. See? Shadowrun is cross-play".
Yet, as time went on, it became painfully obvious that Microsoft was reallocating resources to the console side of things because that's where the money is. They attempted GFWL -- which bombed -- and after that point their PC support dropped off even further. Microsoft played a huge role in getting formerly-PC-only devs over to consoles because that's where the money was. There was quite the outcry. I remember. Microsoft didn't care, and Microsoft did a very poor job of supporting PC gaming during this period of time.
In the XBox One's case, we have this exact same situation. Console gaming used to be a much bigger market for Microsoft. But the X1 isn't selling what they wanted, Kinect 2.0 didn't grab the so-called "causal market", they're fighting tooth and nail with price cuts and bundles for neglegible gains, and Xbox Live subscriptions have lost their momentum. PC gaming, on the other hand, is coming back in a big way and is becoming far more lucrative. Microsoft as a whole wants to have their own walled store like Apple and Google do, a place to not only put games but to put apps and productivity and enterprise software. THAT's the goal, and even the defenders in this thread would agree that's the focus here.
So what will Microsoft do?
Are they "focusing on the ecosystem" because they see a bright future for the Xbox One and they want to use the PC as a way to make the Xbox One's library stronger?
Or are they doing exactly what they did to their PC gaming efforts a decade ago?
I can sympathize with those who choose to be hopeful, but those same people should at least acknowledge how this looks instead of trying to handwave this away as a "totally different situation. Xbox One isn't losing exclusives. This is a totally different thing". Uh huh.