Take this with a grain of salt, but Marvel Studios may be doing the unthinkable: returning to a filmmaker from one of their movies that they ditched for a new, hot, cheaper filmmaker on the sequel. While that may be a bit over-dramatic, there is a rumor floating that Kenneth Branagh may return to the MCU to direct THOR: RAGNAROK.
According to Heroic Hollywood's Umberto Gonzalez on Popcorn Talk, Marvel Studios may be turning to Branagh since he is familiar with the THOR franchise and they are without a director for the third entry in the Asgardian trilogy, but it may not be so simple.
I was hearing that Marvel wanted Kenneth Branagh back for Thor 3. But, he just got an offer to direct MURDER ON THE ORIENT EXPRESS at Fox. So, I don't know if it is going to happen or not. They're thinking about bringing him back into the fold.
MURDER ON THE ORIENT EXPRESS news came down earlier this week and would definitely fit into Kenneth Branagh's wheelhouse as a filmmaker. Disney has a good relationship with him after the box office success of CINDERELLA, so there could be a way to bring him back but likely at a much higher salary than he had on THOR.
I have found both THOR films to be overrated and underwhelming. The scope for THOR: RAGNAROK, as indicated by the title alone, may be bigger than Branagh can handle as we saw his eye for action didn't quite gel with JACK RYAN: SHADOW RECRUIT. It would make sense for Marvel to bring him back, I just don't know if they actually will.
THOR: RAGNAROK is slated to open on November 3, 2017.