Regarding the CG characters Singer had this to say to MTV when asked about the current technology:
"A CG Nick Hoult or a CG Ewan McGregor, maybe 20 years from now might be perfect, but it’s a little tough on the eyes when it’s not real. I definitely want to use this technology again, and I might even be using some of it in a different way in X-Men. I don’t want to say how, yet, but I’m definitely using some of this technology on X-Men, which I never used in any of the other X-Men films."
Now, regarding Storm's return he basically said he wasn't sure if he wanted to use the character or not. He confirmed that each returning character plays a vital role in the story, but he isn't quite sure where Storm fits into the mix.
“I can’t say. 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.”