I don't care if it's Phoenix Saga or no Phoenix Saga, Angel or no Angel...they need to bring that cast back by any means necessary. Singer leaving sucks ass, but they could certainly do worse with the replacement. Xavier being played by someone else besides Stewart after the first two films...ugh.
And please let this be the last one. If they keep doing them, one is going to suck eventually.
A full version of the audiobook with all of the stories was just released a few weeks ago. http://www.amazon.com/World-War-Complete-Edition-History/dp/0804165734/ref=sr_1_1?ie=UTF8&qid=1372110098&sr=8-1&keywords=world+war+z+audiobook