Hopefully history will repeat itself. From ProBasketball News
Historically, whenever a superstar or rising player is traded, his old team doesn’t get back equal value or a fellow superstar and his new team gets an energetic, hungry player who just needed a change of scenery.
Ray Allen and Kevin Garnett are expected to give Boston more than that. They’re expected to bring a championship right away or in the near future.
History is on Boston’s side.
Many greats who have been traded either have brought their new teams a championship in their first seasons, brought a title within a couple of years of their arrival or gotten the squads to the Finals in Year 1. And many of the players have won the MVP award.
The article goes on to site several examples.