If you read the article, it's 41,000. And it's being built with future expansion in mind. It wasn't that long ago ISU had an official capacity of 43,000.
CSU doesn't draw well. I don't see the on-campus stadium giving them much of a boost.
It is interesting that CSU wants to play the CU-CSU game in Denver because of the money and can't sell their own allotment of tickets to the game. If most of your alums are in the Denver area and won't go see a game against an instate rival, why would they drive 75 minutes to go to an "On-campus" stadium to play Nevada or someday Iowa State?