Very few in Denver care about CU. If CSU can string together some strong seasons, they should be able to grab a good portion of a decent size media market (17th largest in country).
CU's football team has been an embarrassment for years. I think that CSU has a great opportunity to build something. It sounds like they are putting in that investment. They have a long ways to go, especially with declining football attendance (Only about 19K this past year).
If they start winning a lot and can get good momentum in the Denver market, they do have some potential. They certainly have a long way to go at this point and are probably a long shot (CU averages 38K fans per game, so they are still much smaller). I would say that it will take at least 5-10 years for CSU to make the strides necessary for B12 to invite them.