The possible arrival of both Metzelder and Heinze means that Real Madrid wouldn't pay more than around 7 million Euros, as the former is free. So, I can see them still want to capture Milito. Another thing, maybe Cannavaro hasn't convinced them during the previous season and they want to get rid of him, especially after taking into consideration that Capello would possibly leave. Hence, their back line will be consisting of:
Ramos - Metzelder - Milito - Heinze
Maybe this is what they're thinking about for the next season, who knows?