I'm starting to think the BYU-Colorado State tandem has a real chance of being chosen.
Here are some interesting statistics about combined statistical areas:
CSA/CSA Rank/2015 Population/Population Change from 2010
Denver-Aurora/16th/3.419 million/
+10.61%
Salt Lake City-Provo-Orem/23rd/2.468 million/
+8.63%
Cincinnati-Wilmington-Maysville/28th/2.217 million/+1.96%
Hartford-West Hartford/37th/1.483 million/
-0.22%
Memphis-Forrest City/41st/1.371 million/+1.30%
https://en.wikipedia.org/wiki/Combined_s...ical_areas
The combined population of the Denver and Salt Lake City CSAs is more than 50% larger than the combined population of the Cincinnati and Hartford or Cincinnati and Memphis CSAs. And the difference in growth rates is eye-catching.
Of course it's not just about population -- if so Houston would be a slam-dunk for an invitation -- but the Big 12 already (mostly) owns the Texas market. The question is, does the Big 12 want to take on the Big 10 in Ohio and the Northeast, or does it want to take on the Pac-12 in Colorado and Utah? I'm thinking it's better to take on the Pac-12, especially given the historical rivalries between Colorado and Colorado State and between Utah and BYU, which have the potential to draw substantial fan attention if they become P5-level rivalries. I don't see rivalries between Ohio State and Cincinnati or between Rutgers and UConn having the same potential for generating TV ratings.
As for Colorado State not being "P5 worthy", the school does have a few things in its favor. Academics is strong -- Colorado State is a top-level research university -- and the school is building a brand new on-campus stadium. It's true that Colorado State's football attendance isn't impressive, having averaged just 25K in 2015, but Kansas averaged only 27K. Put the Rams in the Big 12 and they would probably sell out their new 36K-seat home.