I think the problem with Missouri is their admin has been very fickle over the years. Plus they haven't been a top drawer program athletically. The Big 12 feels they more than make up for what they lose in Missouri if they hang together and make the deal with the PAC 10.
Missouri fits the bill for the Big 10 academically, which is a big deal with them, and they are acceptable athletically. Ohio State won't mind having another team in the conference they can whip up on.
More than likely, Missouri gets a soft landing no matter what happens.