Bryan Singer is gathering mutants past and present for the upcoming "X-Men: Days of Future Past," but there are two big names he isn't quite sure will be making the return to the franchise. 

Among the former "X-Men" stars who will be appearing in "Future Past" are Hugh Jackman, Ellen Page, Anna Paquin, Shawn Ashmore, Patrick Stewart and Ian McKellen. Through the film's time-twisting plot line, they'll share the screen with "X-Men: First Class" stars James McAvoy (Professor X), Michael Fassbender (Magneto), Nicholas Hoult (Beast) and Jennifer Lawrence (Mystique). 

However, Halle Berry and Alan Cumming may not be reprising their respective mutant roles as Storm and Nightcrawler.

"I can’t say," Singer told MTV when asked about Berry's possible return as Storm, “I don’t know yet. And it’s not necessarily a deal making aspect at all. I want to make sure it’ll make sense. But I love working with her.” 

When asked by Huffington Post about Nightcrawler, he gave a similar answer, saying, "Sometimes you don't want to say 'yes' or 'no' to something that may not be a 'yes' or a 'no,' or anything. I haven't decided yet, a few things. I'm still, you know -- there are certain aspects of the script that I'm still toying with."

Berry played Storm in the first three "X-Men" films, while Cumming joined as Nightcrawler in 2003's "X-Men 2: X-Men United," which was the last mutant superhero film directed by Singer. 

Do you think Storm and Nightcrawler need to be in "Future Past"?