Only a couple of days after Cadena SER reported that Casillas will stay with los blancos while López could join Napoli, Marca run the same story on their frontpage. It should be noted that Iker Casillas' girlfriend, Sara Carbonero, writes a column for them, so they could definitely have some insight information about Casillas' decision.
Apparently, the goalkeeper would've told Florentino Pérez that he finally wants to stay, with Real Madrid's President replying the following.
I want you to stay and I will not let you go anywhere, so done deal!
Marca also report that the goalkeeper decided to leave the club last August, when he saw that Diego López was going to start in the Liga BBVA games. With Casillas in goal, it would be interesting to sign a young goalkeeper to learn how big of a club Real Madrid is and wait for his chance when Iker decides to end his career.