This needs to be clarified further. Trading for Jimmy Butler, in a situation where we also acquire KD and Horford, is very complicated.
For starters, if the salary cap is $92 million, we would be about $600k short of the room needed to sign Horford and KD to max deals, even AFTER getting rid of Amir and JJ (and John Holland), and renouncing all of our free agents. So someone has to be moved out.
If Butler is traded for, there are two ways. Firstly, he could be traded for on draft night. This is an easy trade to make for salary matching purposes. However, it means he'd already be on our roster when KD and Horford are signed, so you'd need to send out 2016 salaries that equal his 2016 salary (or actually exceed by $600k, as described above). Furthermore, he has a 5% trade kicker, meaning his 2016 cap his is a little over $18.3 million. So we'd have to send out approximately $19 million in salaries to fit him and have room for the other two. That's a LOT to send out. Bradley, Rozier, Hunter, Young, Mickey, and #3 combined are not enough. You're still short by over $2 million in salary (since you'd now have 9 players on the roster and need to allocate a $547k cap hold for each roster slot below 12).
Alternatively, you can sign KD and Horford (remembering you still need to clear $600k), and then trade for Butler. In this scenario, you have to send out $13.3 million in salaries to match. However, the #3 pick (or #16 or #23) DO NOT count as part of this $13.3 million, unless the trade is made 30 days after any of the picks are signed (which is why the Wiggins deal was completed in August 2014 instead of July). In this scenario, Bradley would have to be traded with all four of Rozier, Young, Hunter, and Mickey for it to work. But recall you've also had to shed $600k salary already, so presumably it's been one of the kids who's been moved. Now you don't have enough salary to trade for Butler, since if you've dumped Hunter, who's the cheapest, you're short by $147k in matching salaries.
So the other choice is to trade for Butler in August, but if you're using the acquisition (or pending acquisition) of Butler to lure KD and Horford, that isn't an option either.
It's really difficult to trade for Butler, and the cost is very steep to make the salaries work. Bradley, Young plus the three rookies, the #3 pick, and something else to create the appropriate room. Is it impossible? No. But it is not something we should expect. And given the cost, I'm not sure it's something we should hope for, either. Our roster would consist of KD, Horford, Butler, IT, Crowder, Olynyk, Smart, the #16 pick, whomever we could sign with the room exception of $2.9 million, and a host of players in minimum contracts, be they our second rounders or veterans. It's really a nice top of the rotation, but it's really shallow, and very small in the frontcourt. It'll be tough to even carve out a 9-man rotation of non-replacement level talent.