Apparently he's getting some practice there with Rolen going to the DL
Personally, I like this idea. I've never been impressed with Francisco and think he's best used as part of a trade. The Reds need a third baseman for the future and Yonder has shown some good ability with the bat already. He's clearly more comfortable in the infield than outfield as well.
I can see Yonder hitting 4th or 5th while playing regularly at 3rd in 2012 with Frazier as his backup and Cairo coming off the bench to backup Votto at first.