TLDR; For some folks, the above may be all you need to hear: you may be dropping your coffee and donuts now to get the update applied. Still others will see this "huge post" and think, "crap, I don't have time for this". For you, skip to the bottom and its "concluding key points". You can then decide what you think you do or don't "need to know" and pick and choose from the sections as you like.
Finally, for those who prefer because of the importance of all this to be led more carefully through understanding things (in a way that's worked for the many people I have helped so far this week, and is far more than either Adobe or Hackernews has shared), please do read on.