IMO a big part of what made Thor work was Branagh's Shakespearian experience, and the fact that Marvel has had a 'revolving door' policy for the sequel hasn't exactly been encouraging. I could see Neil Marshall doing good stuff, but the list of ideal Thor directors isn't exactly a long one.
I feel I've said this here before, but once more for the cheap seats - in a perfect world they'd be slapping on the desk of either John Milius or John Boorman a blank cheque and a licence to go nuts. A guy can dream...