Prime minister Hatoyama just announced that he'll be stepping down in response to the fallout from the US base mess and the resulting breakup of the coalition. No word on exactly when he's leaving - or if he'll manage to drag Ozawa down with him - but he'll address the members of both houses today.
Presumably he'll tell everyone exactly when he'll step down at that point. Or he'll tell people he's changed his mind and would like to continue, or decide he hasn't decided on the Futenma relocation after all, or fail to show up when he couldn't decide on what tie to wear. Steely resolve has never been his strong point.
Japanese politics may have many faults. Being boring is not one of them, thankfully.
Update: Hatoyama's apparently leaving before the election - as soon as a new leader (Naoto Kan, presumably) is elected. More significantly, Ozawa has agreed to step down as well. The end of an era, and of one of the more interesting political operators in Japan.