When the first round of bids are submitted by Jan. 23, the Celtics expect to have received at least four and up to five from investment groups vying to become the next owner of the NBA franchise, according to a source with direct knowledge of the sale process on Thursday. One of those bidders is a consortium led by current Celtics co-owner Steve Pagliuca. The Grousbeck family expects the ultimate price to exceed $6 billion. All members of the bidding groups have been vetted by the NBA. Identities of the control person leading the other three to four groups remain under wraps.