Brad Bird could be interesting. I enjoyed Ghost Protocol (it's not better than the first or third films but it's way beyond the second - but it's a skoosh weak on the villain front and has some dodgy CGI. It's biggest asset is the Burj Khalifa sequence) quite a lot but he's already got his next film lined up called '1952' which is set for Dec 2014 release just now.
Of course he was also rumoured for Star Wars as well. That could have been interesting as well. But he supposedly has his own dream project he wants to get made as well ('1906') which is meant to be a megabudget project. So he may not be available. Of course it still depends whether a third film even goes forward.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist