I just read the interview with Gillen about his 4 issue story of " Thor goes to Hell" coming up between issues 611-614.
It looks really interesting what he will do considering this is not Gillen tying up any loose JMS plots or Siege issues. This will be his own story.
It seems that the Fraction/Ferry issues will start with 615 as Ferry has been given more time to get his art updated in time for the start.
Here's a link to some of the designs:
So, Fraction or Gillen ?