The San Jose Mercury News's Jon Wilner is reporting that Colorado is likely to accept a Pac-10 invitation today. As in, a day before Nebraska is supposed to formally announce its Big Ten membership.
Also according to Wilner, the five other rumored schools (Texas, Texas A&M, Texas Tech, Oklahoma, Oklahoma State) are committed to joining the Pac-10 together if Nebraska bolts. So yeah: the SEC's talks with Texas A&M don't appear to have added up to much.
If somehow the Big 12 stays together despite losing Colorado and probably Nebraska, the Pac-10 would add Utah to get to 12. That's the story out of San Jose.