Fortunately so far the idea of Aslan being voiced by Meryl Streep is just a rumor. It is NOT confirmed. Surely common sense will win out.

To "Rebecca" I understand what you're saying about gender but nonetheless God created gender, refers to himself biblically as "Father" and Jesus was male. We're ALL created in his image, male or female, but to take Aslan, the only character in every book, and turn that upside down would disrupt it's core conceptional narrative.