NBC News is reporting that Justice David Souter is, in fact, planning to retire, either at the end of this term or when his successor is confirmed.

UPDATE: More from the AP:

Justice David Souter has told the White House that he will retire from the Supreme Court at the end of the court's term in June, a source familiar with his plans said Thursday night.

The source spoke to The Associated Press on condition of anonymity because he was not authorized to speak for Souter. . . .

National Public Radio reported that Souter will remain on the bench until a successor is confirmed.

The Supreme Court declined to comment on the report.

SECOND UPDATE: From the NYT:

Two friends of Justice Souter, 69, said Thursday night that he had often spoken privately of his intentions to be the court's first retirement if Mr. Obama won the election last fall. He has told friends that he looked forward to returning to his native New Hampshire while he was still able to enjoy climbing mountains and other outdoor activities.