Subject: How does one proceed when all of the board terms have expired?

I am one of three incorporators of a 501(c)(3) that has been dormant for the last year and a half.  Rather than close the foundation down, we plan to restart it under a new name and management (the mission will remain substantially unchanged).  All of the incorporaters are (or were) board members.  But the board terms were all for two years, and all terms have expired.  Presumably any change in management structure will require action by the board.  The question is, who constitutes the board for this purpose?  Is it necessary to obtain the formal resignation of board members who do not plan to remain on the board?  Can the incorporators constitute the board for this purpose?