On Saturday night, shortly after Markelle Fultz worked out at Philly's practice facility, Aldridge tweeted the deal will be finalized on Monday, with the top pick going to the Sixers, who will take Fultz.
Trade between Philly and Boston will be finalized on Monday, per source. Sides have agreed. Sixers will get first pick and take Fultz.— David Aldridge (@daldridgetnt) June 18, 2017
Additional reports confirmed the deal, including from Adrian Wojnarowski, who noted that the two sides have been locked into the deal for 24 hours and that Fultz would not have worked out for the Sixers without assurance that the deal was essentially done.
Sixers needed Fultz workout/meeting to complete deal w/ Celtics and, as expected, sides have deal for No. 1 pick. Trade call planned Monday.— Adrian Wojnarowski (@WojVerticalNBA) June 18, 2017
Wojnarowski also reported the Lakers attempted to deal for the top pick, but the Sixers had a better package to offer the Celtics.
As for how Fultz feels about the trade, Marc Spears is saying that Fultz loved the Lakers but is "good" with going to the Sixers. Via ESPN:
"Washington guard Markell Fultz REALLY loved Magic Johnson & the Lakers, but is good with going to Philly, a source said. Lakers have 2nd pick."
We also now know what the Celtics will be getting back in return from the Sixers. According to Wojnarowski, it will be two first-round picks, including the No. 3 overall pick in this year's draft.
Clarification on deal: Besides its 2017 FRP, Philly sends '18 Lakers pick w/ protections. If it doesn't convey, 76ers send 2019 Kings pick.— Adrian Wojnarowski (@WojVerticalNBA) June 18, 2017
The protections on the pick from the Lakers is of course the key here, as it will determine whether the Celtics have an extra first-round pick next year, or in 2019. Regardless, it should be a high pick, as both the Lakers and Kings figure to be at the top of the lottery in the next few seasons.