Davis is sure to attract plenty of suitors, but because of his contract, some teams are not capable of trading for him. It's not that Davis makes too much money to make the numbers work on a deal, but that he's on a specific type of rookie extension that prevents him from being teammates with certain players.
Following Derrick Rose's MVP season in 2010-11, the NBA went into a lockout to renegotiate the collective bargaining agreement. In the new CBA, the "Derrick Rose Rule" was put into place so teams could more appropriately compensate young players who come out the gates and prove to be elite talents.
When a player was eligible for his rookie extension, teams were allowed to offer the player up to 30% of the salary cap for a single season as the max contract if the player had been voted an All-Star starter twice, made an All-NBA team twice or won the league MVP. Prior to this, teams could not offer more than 25% of the salary cap on an extension to a player with so few years of service in the league. The rule was slightly adjusted with the most recent CBA so that a player is eligible if he makes an All-NBA team or wins Defensive Player of the Year in the season preceding the first season on the extension or in any two of the three seasons preceding the extension, or if the player wins MVP in any of the three seasons preceding the extension.
In addition to the "Rose Rule," there is the Designated Player Rookie Scale Extension that allows teams to sign a player to a contract that covers up to six seasons from the date it is agreed upon. Teams are allowed to have two Designated Rookie Scale Players at a time, but they are only allowed to acquire one of them by trade.
The Boston Celtics, who have long been considered one of the most likely trade destinations for Davis, are not in a position to make a trade right now because they acquired Kyrie Irving by trade. Irving and Davis are both on Designated Player Rookie Scale Extensions, so the Celtics would have to give up Irving if they wanted to bring in Davis.
Another option for the Celtics would be to just wait until July 1 when Irving is expected to become a free agent. At that point, Boston could trade for Davis and just re-sign Irving to a new deal.