Iowa hasn't been to a Sweet 16 in 24 years. There have been something like 120-130 teams that have made a Sweet 16 in that time period, which means it isn't an impossible task.
And your "Who's the next coach you can guarantee will get Iowa to the Sweet 16" is a cowardly and, to be honest, dumb argument.
Of course there are no guarantees....but not making a change because of fear of failure guarantees you won't experience increased success, either. That's a losers mentality.
And no, I am not calling for Fran to be fired.