Having told Marca on Sunday that the Portuguese winger staying at Manchester United was "the most likely scenario" he has now told The Sun he would place a bet on Real signing him.
When asked if he would put money on Ronaldo joining Real, Calderon - who will meet United chief executive David Gill at the European Club Association summit in Switzerland on Monday - said: "I would bet."
He was quick to add, though, that the decision rests with Ronaldo himself, saying: "It is up to the player. If he wants to come, then he can join Real Madrid.
"Manchester United are saying they do not want him to leave and they are not a club who normally sell their best players.
"But if a player wants to leave it is difficult to keep him. It is the same for me. If I have a player who wants to go somewhere else, we let them go."
Calderon had told Marca: "Once Manchester decide they want to sell and they tell us this, then we will say that we're talking about a transfer.
"But today that's not happening and therefore this is a situation that may end up as it is now, as nothing, and Cristiano Ronaldo will continue at Manchester next year.
"At the moment, that's the most likely scenario. They (United) don't want to sell so we can't do anything."