Raul also was on that type of contract aswell, so maybe Madrid would honour his wishes if Casillas is dead set on playing regularly, an agreement so to speak.. he would be on big wages, so Real might be tempted but to be honest I can't see it to be honest..
On a side note, in that article the last paragraph read..
"As a young boy, Casillas cost his parents 1 million after forgetting to post his dad's pool predictions on the weekend, his father correctly predicted all 14 scores"
Lucky he made it as a professional, otherwise there would have been some tension in the Casillas household!