If an XB1 game goes to or is on PC and (A) you have to validate it as a "Microsoft Exclusive" or (B) you care because it reduces the value of your console, then you either have (C) a serious case of buyer's remorse represented by post-purchase rationalization or (D) you determine your self-worth based on circumstances surrounding a piece of plastic and the multi-billion dollar company(ies) that sold it(them) to you.
That's not to say it doesn't reduce the value of the console because it does, but that should only matter to those who are considering purchasing it.
But I guess since this is a sales site, if you're looking at it from a sales perspective then yeah its forgoing the console for the games sales, and its a matter of convenience preference which one you follow.
The game will be available on two platforms. PC is neutral ground and isn't apart of the console war. Sony isn't getting it but it's still multiplatform. Look at how many games are multiplatform and Nintendo never got their own version.
From the standpoint of a consumer product if it is avaliable on another platform, then the need for both platforms with respect to that game is shared. Ergo, the platform's value with respect to that game and by extension those who by that game is reduced. This should be obvious.
The console war is an abstraction where we consider the relative worth/value based on library, services, and other preferences between the consoles. Perhaps, I should make an addendum, because from the standpoint of the console war, it hasn't "lost value" although in the terms of the gaming market, it absolutely has. That's where I was considering it from.
CIP, I really wanted ROTR, I now have ROTR, I still don't have an XB1. QB is now coming to PC as well, I have even less of a reason to buy an XB1.
Not to mention, it gets really hard to justify another console, when they both for the most part do the same thing and have the same costs.