I wouldn't worry about who you get for a narrator. The list always has excellent voices. Don't pre-judge a narrator, especially if you want some day special, like Xmas eve.
Case in point, I planned out our days and hoped for a great narrator our first year. I was dissapointed when the list of narrators was released and I got someone named Joe Mantegna. "Who?" I thought. Well, not wanted to screw up my carefully planned itinerary, I just resigned myself to it.
Did I feel like a fool when CP was done! Joe was an excellent narrator with a fine speaking voice that was the perfect depth and quality for the story of Xmas.
Now, I just pick a date that works around our other plans because I know that any narrator Disney asks will be fabulous.
I also concur with timing that the packages are released in late August/early September.
But there have been years when the narrator list has not been released until October. AND you have to expect that changes can occur in the list up until the date of performance. It's happened at least once every year since I have been watching the CP narrator lists.