The Celtics very well might use a few of their picks to trade up or to trade for an established player. However, if they keep all their picks, they probably won't want to bring in 4 new rookies to an already young roster. So it would make a lot of sense to draft and stash a player or two.
It's obvious the team won't employ all those picks and will utilize some as trade assets, but don't be surprised if Boston uses some of its less glitzy selections to target potential future contributors. Boston could utilize some of if its second-round surplus to take swings on players that won't necessarily land on Boston's roster -- not now, anyhow -- but might compete for a role down the road. The Celtics could lock up the rights to a raw, intriguing young player, then ask them to spend a year or two overseas trying to improve their skills in a setting that will offer more playing time (all while having the ability to bring that player in for offseason activities).
Consider this just another option for Danny and the Celtics front office to ponder on draft night.