Its not so much the possibility of a lockout that has players running, its the type of contracts that will be presented under the new agreement. Ideas that have been suggested include non-guaranteed contracts for all players, or maximum term of 3 years only.
So by opting out now, Pierce leaves $21M on the table, but would hope to sign a 4-5 year deal guaranteed for $60-70M - which survives no matter what happens with the new CBA. And if the Celtics don't want to re-sign him, I am sure someone like the Clippers wil pay that amount.
Obvioulsy the agent for Richard Jefferson has got strong indications from somewhere that he will be offered a 4-5 year deal worth much more than the $15M he is giving up. Maybe $8M per year?
Aside from base salary, there are other sources of income for an NBA player - a % of all revenue made from merchandise (basketball cards, t-shirts etc) gets divided up evenly amongst the NBA Players Association; Extra bonuses from Playoff participation; NBA Superannuation or pension;
So the longer a player is in the league, the more he can potentially earn outside of his base salary. And with the possibility of non-guaranteed contracts in 2011/12, 5 years guaranteed looks pretty good right now.