Figgins has agreed to do so. Not that he'd really have a choice, and it's silly to think he wouldn't want to.
Though he bounced around during his days with the Angels, third base is quite obviously Figgins' best position.
In 2008 and 2009, Figgins posted a UZR of 10.6 and 16.6 in each year respectively. For the Mariners in 2010, Figgins' UZR at second base was a meager -12.3. While UZR is a dish best served after two years of aging, it's quite obvious he's better suited to the hot corner.
This now opens the door for newly acquired Brendan Ryan to start the season at second base until Dustin Ackley gets the call. At that point, Ryan can slide over to shortstop if—when, Jack Wilson gets hurt.
Who knows if this will lead to Figgins being more comfortable and thus a return of some of his offensive value? It surely can't hurt, though.