I wouldn't be surprised if we do hold DDG to see him sign another contract with a gentleman's clause. People talk about letting your deal elapse as if its nothing, but massively so for a goalkeeper, its a real risk. If DDG lets his deal run, and then suffers a big injury in Dec for example, say a knee like Valdes, where would that leave him? That 200k p/w isn't going to be on the table here, and Real might not want to sign a goalkeeper who may or may not get back to peak form 12 months later. I think it would be insurance for him to sign a deal so he knows he's getting paid, but if Real come in he's not tied in the same way.
That said, Real's deal might not mean all that much. If Navas came in to fight for the number 1 spot, much like Ospina at Arsenal. The departure of Casillas and the arrival of DDG could just signal he's on permanent bench duty, so the new signing could just be his replacement.