I think by the time Calhoun retired, they had a healthy level of respect for one another. They weren't buddies by any means..but the respect was there.
Probably more interesting, is the relationship Calhoun had with the women's players and what Geno had with the Men's. Calhoun loved Taurasi and Moore. And I remember Geno trying to help Okafor with his free throws..and the smile he had on his face while talking about Kemba Walker not to mention how much he loves Ray.
I think Geno and KO will be/are fine. In fact, earlier this year Geno was quoted as saying he thought KO should be coach of the year.