it's not a certainty that they willingly sell to ranadive's group, but the nba has its trusty "in the best interests of the league" clause. it's an ace in the hole, and allows them to apply a certain amount of pressure, should the maloofs resist the sensible path of selling to ranadive and co. in such an instance, it is perfectly within the league's province to swoop in and purchase the team, thus paving the way for ranadive to pay the league the cost for the team...
edit: that said, i fully expect the maloofs to accept the sacramento group's offer, however grudgingly they might do so. they're broke. they're itching to buy back into their beer distributorship. they can't hang on to the team anymore, and everybody's wise to their act. the minute they signed a binding agreement to sell to the hansen/ballmer group, they were officially on their way out the door. no turning back, and all that...