Bill Chisholm will assume the Boston Celtics’ governor role as soon as the National Basketball Association approves his $6.1 billion purchase of the franchise, according to multiple league sources and media reports. The change abandons a succession plan announced in March that would have kept current governor Wyc Grousbeck in charge until the 2027-28 season. Under the reworked arrangement, Grousbeck will stay with the club as alternate governor and chief executive officer through 2028, but Chisholm will take over day-to-day control once the deal closes. The transaction calls for Chisholm’s group to acquire 51 percent of the team immediately, with the remaining shares scheduled to be transferred in 2027-28. The NBA’s board of governors is expected to vote on the sale within the next week. The agreement, initially valued at a record price for a North American professional sports franchise when struck, has taken roughly five months to reach the approval stage, longer than several recent team transfers.