I think you should always tender an offer and see what happens.
There are some teams over the salary cap, and I can see a team like Cleveland possibly being interested in Ben, seeing that LeBron was a huge Ben supporter coming out of college.
A team may offer a second round pick to assure we won't match. Therefore, they can offer a more market rate contract, instead of overpaying for BMac, to make sure we don't match. That way they save on spending on Ben's contract and re-assuring they get him with a 2nd round pick.
I think it depends. If Ben wants to move on and the Kings have no intention of re-signing him then you're just making it harder for him to find a new team for the slight chance you can squeeze a late 2nd in a sign-and-trade. That's something an agent (and other agents around the league) will remember.