I'm pretty sure we can rule out Beauty & The Beast, Bambi, Snow White, and Lion King, as they are all currently in the vault, and the majority of the other major Disney titles have already been announced (Fantasia, Peter Pan, Lady & The Tramp, 101 Dalmatians, Dumbo etc), so we can whittle the list down considerably!
We also know it won't be #6-#11 (not very likely!), and there's also a big chance that it won't be a title like The Rescuers, The Rescuers Down Under, Basil The Great Mouse Detective, Oliver & Company, The Black Cauldron, or The Many Adventures Of Winnie The Pooh - These are usually among the last to get released on any format (based on past releases). I also doubt very much that they'll delve into the post-1990's titles after Tarzan just yet, especially as the majority of the 2000's titles have yet to be released on Blu-Ray in the UK so far. My money says Zavvi will stick to the earlier titles which are already established as family favourites and good sellers
This leaves us a short list to work with:
#2 - Pinocchio
#12 - Cinderella
#13 - Alice In Wonderland
#16 - Sleeping Beauty
#18 - Sword In The Stone
#20 - The Aristocats
#21 - Robin Hood
#24 - The Fox And The Hound
#33 - Pocahontas
#34 - The Hunchback Of Notre Dame
#35 - Hercules
#36 - Mulan
#37 - Tarzan
My bet would be one of the first eight on the list above - Probably Robin Hood or Cinderella, although a Sleeping Beauty SteelBook has recently been announced for another country, so that could also be next
Personally, I would like to see all of the above released before Zavvi even consider releasing any of the newer titles, although I would also like to see some love for The Rescuers and some of the 80's Disney titles which most people forget about