Maybe it's just me but Michael Caine should play M because if this movie gets made, he's likely be 85-86 years old and the role of a secret agent may be too physically demanding. As the leader of MI6, it may be a better fit.
I also wonder if when Nolan will take the franchise, he will completely departure from previous installments. I'm pretty sure we'll have a new Bond, but will he keep M
and Q (Peter Whishaw who's only 31, so he could keep the role very long)
I understand people who wants Nolan to have complete control on this but I think he needs to respect the franchise