Will hold off judgment on the course changes until I see it. I guess the first time we will see the new course is when they file with USTA to certify the course? I seem to recall that happens a few weeks before the guide comes out.
First time I ran the marathon (2008) we ran through world showcase at the beginning and I would be happy if they brought that part back. While we get to do it for the 5k/10k, I love running through that area in the dark. I also think I remember hearing how in one of the early years they also ran through Blizzard Beach (I also remember hearing about them having it "snow" during that part, which would be cool), but my memory ain't what it used to be. Not sure if anyone has course maps from that far back...
Start time change doesn't bother me. If it's hot again, it is 30 minutes less in the sun, which I am happy with. Already had to get up so so so early, I will trade the 30 minutes less sleep for less time in the sun. Also could give more people a chance to get to the castle while it's still dark (assuming they don't change the course that much). I typically don't do rides during, but again, depending on where they make the course changes, the early start might not be that much of an impact (if they get added before AK).
I agree that if the "open air" runner area is the replacement for the race retreat, I'm likely out. I splurged for RR as insurance against bad weather (cold/rain), so no need if it's all outdoors now.