On the NDSU Football Show, they had Matt Larsen and a segment on the future IPF (~17:00).
Synopsis: It has a 70' ceiling, dimensions are 60 x 120 yards, and the price tag is $37.2 million. The Legislature still needs to approve the project. If that goes through, the earliest start date is this time next year.
I wouldn't be surprised if we see that raising money for a new building is easier than raising money to refurbish an old one.