To a degree, it depends when. If it's 2001, maybe LSU. If it's 2008, when SEC had first dibs on a one-loss spot, obviously LSU. But yeah, Clemson is in.
Good thing there's a playoff.
EDIT: Actually, this brings up an interesting side thing. If there isn't a playoff, are we speaking glowingly of Clemson right now? IN my youth, every massive winning streak had all sorts of meaning heaped upon it. But these days, not so.