Since you probably lose 6-8 players from the 2016-17 roster, 6 new guys looks like a minimum. Moreover, 4-5 of those guys are likely starters, so the haul has to include a lot of top players.
In case you are wondering, I'm looking at these guys leaving. Maybe not all of them, but could be all of them. Am I missing anyone?
Giles
Tatum
Bolden
Jackson
Allen
Jefferson
Jones
Pagliuca
Obviously, Jefferson and Jones are no-brainer's as their eligibility will be used up. It's also safe to assume that both Giles and Tatum leave after one season. In addition, it's believed that Grayson will also likely move on with a degree in tow. Pagliuca will too be gone, but he doesn't really fit into the mix as he's just a walk-on who won't play, regardless.
So really, the question becomes about Bolden, Jackson, and maybe, to a slight extent, Grayson. The latter guy, Grayson, could return. I don't expect it, but I wouldn't be completely shocked if he did.
I'd be surprised if Bolden is back for 2017-18. Two reasons, 1) he's going to be a high commodity because of his size and athleticism, and 2) he might not see many weaknesses exposed because of the players around him. That lends me to think he goes.
Frank, on the other hand, is the wildcard. He might have first-round promises, but I think his best bet to become a collegiate star is during his sophomore season. The upcoming year may be a feeling out process, and garnering more than 20mpg on average could be tough to come by.
We'll see what happens. I'm going to enjoy the season and hope the best comes from it. If Duke is fortunate to reach their ultimate goal then I think everyone here is willing to trade for it.