The main holdup right now, per league sources, is the protracted sale of the Celtics franchise, which was put on the market last July by majority owner Wyc Grousbeck. Sources say league officials are eying a sale price of at least $6 billion, in part to set a baseline for the expansion franchise fees (and, of course, in part due to the Celtics being one of the marquee franchises in pro sports). But that hasn’t come to pass yet, and the team remains for sale.