I think people need to realize how much harder it will be (and it was already tough) to trade for young stars with the new CBA in place. They have even more incentive than before to re-sign with their current teams, so I doubt we'll see any of AD, Butler, Paul George, etc. on the move anytime soon. Cousins remains the most likely of the bunch, but I still think he and the Kings will work something out now that George Karl is outta the picture.
If you're the Celtics, building through the draft seems like the best option unless something falls perfectly into their laps. Extend your own guys, bring the Euro guys over, try to land a stud with the Brooklyn pick, and hope Jaylen Brown takes that leap.
It's a tough way to build a contender, but it looks like the most realistic avenue due to the new CBA.