While THOR didn't return huge profits at the box office when it was released in 2011, it was surprisingly good. Fans weren't sure what to expect. Branagh's past work made them curious about Marvel's decision to hire him, and people were worried they wouldn't capture Asgard (as well as Thor & Loki) accurately. In the end, it ended up surprising everyone by being a good film.
I thought it was a lot of fun, and I was hopeful Branagh would return for the sequel, THOR: THE DARK WORLD. Unfortunately, that never happened due to scheduling conflicts - although some sources claimed it was because of creative differences.
During a recent interview with The Hollywood Reporter, they asked him if, after working with Disney on the upcoming CINDERELLA film, if he'd be interested in working with Marvel again. Here is what he had to say:
I enjoyed THOR: THE DARK WORLD, but it wasn't as great as it could have been. (I don't blame this on the director; I blame it on the fact that the villain wasn't well developed.) I think bringing Branagh back for THOR: RAGNAROK would be a wise decision.
Of course, just because Branagh would be willing to work with Marvel again does not mean it'll happen. Still, I'm hopeful.
Source: The Hollywood Reporter.