Just to be clear, this is not a trade rumor, just one that he said works for both teams. Personally I am not a fan of giving up 2018 Nets pick for Butler.
Per Kevin Pelton:
"Bulls send Butler to Boston
Boston Celtics get: Forwards Jimmy Butler and Taj Gibson
Chicago Bulls get: Guard Terry Rozier, centers Amir Johnson and Tyler Zeller, Brooklyn's 2018 first-round pick and Memphis' protected 2019 first-round pick
View in the ESPN Trade Machine
Even if the Raptors get Millsap, I still think the Celtics might be a bigger threat to the Cavaliers if they can get Butler. Not only that, getting a player in his prime (Butler is 27) and under contract sets up Boston to contend for years. I'd be willing to surrender any non-starter and any draft pick besides the 2017 Nets pick to get Butler.
That might not be enough for Chicago in reality -- I could see the Bulls holding out for this year's Brooklyn pick, which is virtually certain to have the best chance at being No. 1 overall in a strong draft -- but in my fantasy world, the teams make a deal that also sends the Celtics Gibson, an impending free agent who strengthens a Boston frontcourt weakened by the loss of Johnson."