Say what you will about her character (and I'm sure many of you will say a lot), it doesn't make much sense for Storm not to be involved in Bryan Singer's X-MEN: DAYS OF FUTURE PAST, especially if Singer's promise to "fix" the franchise holds true. Plus, I think it's appropriate, if Singer's really trying to bring those two worlds of FIRST CLASS and the original films together. DAYS OF FUTURE PAST is a big story, and the more characters the merrier. Fox isn't going to let X-MEN out of their grasp anytime soon, so it makes sense to build something that will last.
So this brings us to Halle Berry and Storm. According to Indiewire, Halle Berry says she's "practically 90% sure" that Storm will return, although they don't have a lot of room to negotiate, since filming starts in April. They don't have direct quotes from her, but Shadow and Act says that she would be returning to the role in all probability. And many toads were struck by lightning when they learned of this news.
All kidding aside, Storm's too important a character to the X-Men and this franchise. It's only right that the character return. We shall see if this all comes to fruition.