A couple of days ago Quartermaster listed all the Legacies that aren't going to exist after the update.
Each of those legacies is being replaced with specific legacies at the exact same relic tier that they were before. So all your work isn't lost its just not quite the same as you expected.
Some of the class guides in your class section will list what those legacy changes are but not all have been accounted for yet by testers.
Just wanted to get this tidbit of information out to you all.