According to Adrian Wojnarowski of Yahoo! Sports:
Kevin Garnett will agree to trade to Brooklyn and Celtics are sending KG and Paul Pierce to the Nets, league sources tell Y! Sports.
— Adrian Wojnarowski (@WojYahooNBA) June 28, 2013
That was reportedly the last obstacle standing in the way of the trade, in which the Brooklyn Nets will send Kris Humphries, Gerald Wallace, a signed-and-traded Keith Bogans, MarShon Brooks, Kris Joseph, three first-round picks (2014, 2016, 2018), and the right to swap picks in 2017 to the Boston Celtics for Kevin Garnett, Paul Pierce, and Jason Terry. Reggie Evans was originally in the deal, but has been switched out for MarShon Brooks, according to various reports.
The deal will become official on July 10th after the July moratorium.
Wojnarowski adds that the Nets have agreed to fully guarantee Garnett's $12 million in 2014-15. Garnett's contract was only guaranteed for $6 million for the 2014-15 season.