No, I think they had been working on this years prior, but shelved it to work on other games. Lots of games get thrown on the back burner or cancelled before they are even announced. If MS didn't want multiplayer games for gamepass, I'm not so sure this would have ever seen the light of day.
At the E3 colliseum they had a discussion about it, and it basically went like this 'every studio can make what they want and if somehow wants to make a game from our dormant IP's like Conker they can except for the Halo/gears studios'.
You can watch it here: https://www.youtube.com/watch?v=O3rG2vDA4N8 Ninja theory also joined the discussion.