Wonder where they sit with most publishers. At some point others (Activision-Blizzard, Bethesda, 2K etc.) will want to introduce their own, just as EA did. At that point, it might as well be a Win10 box (especially with MS shifting to Play Anywhere), and then I'd wonder if Live Gold disappears in favour of GamePass (many years later).
ahem.
At this point, MS would be getting 2x subs from each member (gold and game pass). They will likely not want to take a revenue hit if they can avoid it so part of what they'll have to do is find a way to balance the value of Gold along with game pass. I'm sure it's been talked about internally.
Blending Gold into gamepass and discount Gold would be a smart option. You'd see the sub attach rates go up and there would be a perception of a discount to the consumer which they like. I'd try to steer in that direction but I'm not at M$ (< see how edgy I am!) so let's see what they come up with.