Here's a quick take from the publisher on what's new:
This edition includes deluxe components (such as an embossed box and lightning-bolt-shaped energy) and all-new art by Paul Mafayon. The game is based on the classic KoT rules, with the addition of a new mechanism exclusive to this edition to offer a fresh gaming experience.
I received an overview of this edition at SPIEL '19, and here's what I can tell you: The title and other relevant information about the game will be printed on the shrinkwrap or other covering material so that when you remove that, you see only the image shown above. The only monsters shown so far are Gigazaur and The King, with the others scheduled to be revealed over the coming months ahead of the game's release.
The new mechanism mentioned in the description involves your ability to move up a new sidetrack on the central game board to grab unique bonus powers, while your overall goal remains the same as in the original game: score 20 points, or be the last monster standing.
As for this being a collector's edition, IELLO's Stephen Vargo told me that King of Tokyo: Dark Edition will have only a single print run, with IELLO still working to determine what the size of that print run will be. The challenge is to thread the needle perfectly so that you have neither thousands of people disappointed that they can't acquire the game nor thousands of copies unsold on your next warehouse inventory, but of course that's the challenge for every publisher with every game they publish, so I wish them good luck with that impossible task they've set for themselves.
The anticipated release date for King of Tokyo: Dark Edition is Q2 2020, and I need to clarify with IELLO whether this title will be released in multiple languages or only English and French.