Finally, the day has come, when the bean counters realized it's much easier to op-up Y to Y+ (and "save money") rather than op-up Y to J, and no I really doubt Y can be upgrade to J once this happens, and you need to be Y+ to be upgraded to J.
It goes to show that they think the good old days of corporations and bankers flying F and J are over, and now most corporations are stingy and will only allow their people to fly Y (or Y+) but you got to be the big guy to fly J.
I would imagine they will toy with the 777-ER Y-seat configuration from 3-3-3 to 2-3-2 and call that "Y+", so seat a little bigger, a little bit better food and drink selection, and that's it. EVA airline did this crap as well and from what I have heard their Y+ demand is decent enough for them to favor it over J.
Makes sense all in all, even with the heavy overbooked flights you op-up at most 15-20 people, and usually you only op-up 3-6 people on marginal overbooked flights. Also, there are many in this world that would pay $500-$1000 USD more to feel "Premium" and recognizing they will never be able to afford the J prices.
It benefits the Y buyers and MPC GR and SL people. For MPC DM and GO that gets decent amount of op-ups to J this is not good news.