It was me.
What we are getting in March is fixes to the current party system which is its own app.
What they are doing, wisely, is building an entirely new party system at the OS level and not as a stand alone app, just like it was on the 360. But that is going to take a long time to finish.
Everything in the XB1 is seperate apps because they were really gung-ho about this "one microsoft" bullshit where everything can communicate with everything. It's a good idea, on paper, but what it meant was making things like the parties an app, and an app requires handshakes with every other app it touches. So if you are in a party of 4 and you all are playing different games the app needs to make handshakes with each game. This usually works, of course, but the more times you have to make requests like that more likely you are to get errors.
Having it be system level, like the 360, gets rid of that. That won't be ready until the fall though. Maybe later. It's a big project.