I think Danny will have to continue to be aggressive on draft day. Maybe a team considers trading a star for some younger assets (e.g. Cousins). Otherwise, maybe Danny can finally get a guy he really likes on draft day by moving up. He's tried to do that the last couple years and has failed to make a deal both times.
If Danny can get that one star prospect on board without having to give up too much of the younger talent the Celts already have (Thomas, Smart, Bradley, Crowder etc), that could make the team look really appealing to a bigger name free agent (Al Horford?) or the next star reaching the end of his deal looking for a new place.
I definitely don't think the team can afford to use all of the picks they've got next year, unless half of them are draft and stashes. If Danny can't work out a consolidating trade or two, he'd better open up some room in the rotation for these young guys to get some real playing time, or else a third of the roster will just be young guys with no meaningful experience wasting away on the bench.
It's going to take time, though. The Celts are winning games but they're still only a couple years into this rebuild.