Actually, the worst case was likely only being with Baylor and Iowa State -- and remember this is before Baylor had football success. The thought was that all the decent teams would be gone -- Texas and likely Texas Tech, along with Oklahoma and Oklahoma State, to the PAC. Kansas and Kansas State were expected to move to, probably, the ACC; though the Big 10 may not have been out of the picture.
With so many teams potentially leaving, you were looking at a situation where the Big 12 would lose its autobid and TV contracts, and trying to backfill with teams from the MWC and CUSA.