Phoenix receives: Avery Bradley, Garrett Temple, lesser of their own 2016 and Washington's 2016 1st round pick
Washington receives: Isaiah Thomas, Reggie Bullock*
Boston receives: Andre Miller, Rasual Butler, greater of Washington and Phoenix's 1st round pick
Why for Phoenix: the three point guard rotation is fun and all, but Bradley would probably fit on that team better, offering more defense and fitting in as a two alongside Dragic and Bledsoe. The cost isn't that steep, as they give up IT and maybe move down in the draft in 2016.
Why for Washington: Beal has another stress fracture in his leg (his third in three years, which is sad considering how exciting a player he's become when healthy) and Washington has been slumping without him. Thomas can help fill Beal's scoring while he's out, as well as lighten the load on both Wall and Beal once Beal has returned.
Why for Boston: That pick is unprotected. Bradley is a young player who's still improving and on a very reasonable deal (especially with the soon-to-skyrocket salary cap) for the next three years beyond this. Unprotected picks are getting a little more rare, but I think it's fair in this instance (especially since neither Phoenix or Washington are likely to have great chances at winning the lottery in 2016 even if they do finish in it). I wouldn't do it for a protected pick -- even #1 protected only. Anyway, this costs the C's one of their building blocks, but it also clears up salary for next summer -- enough salary to almost certainly have room to sign outright two max free agents without doing anything about Wallace. (As it presently stands they're between about $6.5 and $8.5 million away from this goal, depending where their draft picks end up and where the salary cap is. Moving $7.7 million owed next year creates critical space.) This would give Danny the ability to find two stars who wanted to play together and offer them a team to join. He would then be able to use Wallace's contract as the primary component to match salaries for a third star in either a sign-and-trade or traditional trade.
*Reggie Bullock was recently acquired by the Suns in the Austin Rivers trade. However, he can be traded in this instance since the rule is he can't be traded for 60 days if his salary is being used in aggregation with other players to match salaries. However, the Suns can acquire Bradley and Temple just by using IT's salary, so Bullock is fine, and the Suns would wind up with a trade exception for his salary. Furthermore, the Wizards are using the remainder of their Trevor Ariza trade exception to acquire Bullock, and the three players they are sending out are used to match IT's salary.