I kind of hope we get two narrators.  One to do the male roles & another to do the female ones.  This is a multi narrative book, and it switches between male & female roles enough that it would help to have a dedicated male & female reader.
While male & female narrators can alter their pitch to do a passable representation of the alternate gender, it is hard to pull off.  Especially for multiple male & female roles like the book has.
BTW; Yes, I've read the book.  You could get one at SDCC if you followed the @acerocbooks Twitter.  I will likely review this weekend, as I have just finished it, but this is where my knowledge comes from.
Looking through the book, there are 6 different voices in total.  Male & female voices are a roughly equal, if you include the cat.  If you just count humans, there are more female voices.  So we likely will be looking at a female narrator.  If that's the case, I really would like Tara Strong if at all possible.