Rachel Bilson Appearing on How I Met Your Mother --- As the Mother?

Is Rachel Bilson going to be the Mother?
The O.C. alum has booked a guest spot on the 100th episode of How I Met Your Mother as the love interest in Ted's story line, TVGuide.com has confirmed.
"Ted will also get as close to meeting the mom as he's ever before," creator Carter Bays told TVGuide.com of the milestone episode. "I don't want to give it away, but he gets so tantalizingly close, it's ridiculous."

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But let's not get too ahead of ourselves here. Both Bilson's rep and a show rep tell TVGuide.com the gig is just a one-episode guest spot, not a recurring role, like, say Sarah Chalke's was.

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Bilson's casting was first reported by Entertainment Weekly's Michael Ausiello.Do you think Bilson is the Mother or just another notch on Ted's long list of ladyfriends?