I also sent in a support case and they did reply with..... Unfortunately it will not be possible for us to postpone the site update as it is very necessary to be conducted on time to keep the maintenance of the site. However the good thing is that it will last hardly for an hour, so you can use rest of the day to post listings on eBay.
So I guess I'll just use that time to take pictures if needed. Also, I'm going to bulk-relist using the eBay bulk relister...it's pretty nice (have you tried it?) Just remember to change the duration if you are relisting some fixed price to auction.
Anyway I too hope it is just one hour..it was last time the UPDATE fell on the same day as an eBay promotion. Hope WE sell alot!
Cindy