I see meelan get the best CB'S available while we get the rest.
Milan will buy one single CB imo and maybe also buy out Senderos from Arsenal.
They already bought Thiago Silva for 10m euro, who is 24 (not too young to be a starter) and is already a Brazilian NT player. Plus all those who watched him were impressed by him.
Maldini will retire, Nesta's situation is pending but there are chances that he won't play again.
If they consider Thiago Silva a regular and if they buy out Senderos cheaply (they still have Bonera), then all they will need is one WC central defender.
What i wanna say is that there will be enough available quality for both Milan and Juve to improve their defenses.