I don't think it's his play, so the timing isn't his to control.
I think he's been informed that others are beginning a campaign (MoveOn.ORG?) and he's trying to get out in front of it. After all, he has claimed credit for running "aggressive investigations" of BCCI (where he covered up Clark Clifford and other Democrat's roles) and he can't allow something new, whether new evidence or just a new smear campaign, to spill over and damage him.
This may be preemptive, as you suggest.
I have to say, not being an American, that John Kerry only came onto my horizon during the primaries/election period.
I didn't get the impression that he was much of a team player even in his own party. The question then is who or what is so important to him that he would take the risk of starting an investigation only to derail it to cover up for someone? Teddy Kennedy, Cameron Kerry or an anonymous benefactor who saved his behind from bankruptcy?