There is no such thing as a guaranteed top 3 pick, only top 4. The Nets pick will likely be for a top 7 guy. The huge advantage of that is you could potentially get a really good player for like $1 million a year, then you get advantages to resign that player above the cap. So it's not just "is the rookie better than the vet we could trade it for," but "are they a more efficient use of the cap?"
There are plenty of players I would trade the pick for, I just don't think they're available. Beal would be worth trading for even though he's an expiring, but he could walk. We don't really need a guard right now, anyway.
So I'd trade it for the right piece, but I just don't know what we could get that would be worth it.