I bloody hope not too! The good sign is that clearly they can much easier update and revamp Mercury to be a better place to visit - one major thing people asked to happen which was QoL on existing places. Also we will have Sparrows available too which must mean its bigger.
They clearly focused on the one shining light of CoO which was the Saint 14 quest which i bet most people didnt complete or haven't even seen it. Their ability to hook players in on story content is great but they have to back that up now with somehow a near impossible content packed DLC I fear.
I expect the new 6 player PvE activity to be a variation that is 1 or 2 steps better than Vex Offensive. It has to be or theyll get canned immediately.
Other than that, your thoughts on some of the most interesting and harder challenging content is spot on. The issue is having a fireteam / people to do it with I find. I haven't done any Master Nightfalls or Master Nightmares. I haven't even attempted the new dungeon which I know is great.
It's funny how it's gone the opposite way on content cos people got mad there was fuck all to do. Now theres too much to do, people feel lost and dont know what to do or where to start. I'd suggest starting at putting the disc in, helps 😀