I don't think it could be something to take less money overall or to free up enough cap space to sign a big free agent in 2010 (we won't have the money anyway). I think it'd be to restructure so the money's spread out more. I.e., say Pierce would be willing to take 3 more years at about $11 mil a year after this contract runs out in 2011. Instead, he opts out next summer, and takes a 4 year, $56 million extension, thereby not giving up any money, but letting the Celtics pay him $14 mil a year for 4 years instead of 21 then 11 for 3 years. That frees up more cap space and money in the short term while keeping Pierce well paid and locked up till he hangs them up (and giving him a little bonus to defer the money). Plus, he has the security of that money being guaranteed before the 2010-11 season instead of after.
In that regard, it might be a reasonable possibility.