Sam Taylor-Johnson had this to say about her departure:
"Directing Fifty Shades of Grey has been an intense and incredible journey for which I am hugely grateful. I have Universal to thank for that. I forged close and lasting relationships with the cast, producers, and crew and most especially, Dakota and Jamie. While I will not be returning to direct the sequels, I wish nothing but success to whosoever takes on the exciting challenges of films two and three."
The film has been a surprising success at the box office despite rather overwhelmingly negative critical reviews. It's another franchise, it seems, where the fans love it but the critics hate it. Like I said, this isn't really surprising but I think it's perhaps the biggest mistake Universal could have made regarding this franchise, aside from allowing James to pen the scripts.
The movie wasn't great but it wasn't horrible and I credited Sam Taylor-Johnson for a lot of that. The element she brought to the film was a pleasant surprise and she gave it a mood that was tolerable. I think losing her puts the sequels at great risk of becoming gimmicky, corny, or feeling mismatched with the first film. We've seen this with film franchises too many times such as Harry Potter, Twilight, The Hunger Games, etc.. Some films outshine the others while some are downright horrible and it's all the direction. Directors bring a lot of elements to a film and when they depart or enter, they have the power to change the whole dynamic of the story.
Mark my words, that will happen with this franchise. I would go far enough to say each film will have a different director. Given what Sam Taylor-Johnson put up with regarding EL James' involvement, I don't think any director in Hollywood will tolerate her shit for more than one film. It's come out that James feuded with Taylor-Johnson over the ending of the film, the dialogue, and how Christian Grey was portrayed. With that said, I would bet that Universal will seek out a director that has similar ideals to EL James or is willing to tolerate the ridiculous amount of control the studio gave her.